Did I mention that I might update these if I get any more inspiration? :3
Relationship arcs
Taenysic:
-All three are/were aware that the three of them were the rising stars of pilot academy together, and feel some regret that they couldn't have followed that natural progression and become a kickass flying team.
-Now awkward for them to be together again with their experiences since all making them hesitant to connect, much less reconnect, with anyone.
-Jessica feels betrayed by TaeNy that they left her out of the loop about their callings, at the time thought that they were knowingly wasting their talents, still shaking off that perception of them
-Jessica also feels more left out because Taeny had been aware of each other's powers and duties at the time, and thus are currently closer, and she doesn't have that experience of having a Higher Calling with her powers.
-Obligatory "all three go out jet-piloting, get attacked and separated from the ship, stranded on the local jungle planet and have to survive together, will discuss their issues with each other and may or may not deal with them" episode. Will examine how all three of them deal differently with feeling that nostalgic connection before having their differences developed in the meantime shoved in their faces.
-How their relationships with each other are progressing measured by recurring scenes where any combination of them are jet-piloting and having cockpit conversation before a mission.
Data Source:
-Yoona and Sunny were actually roommates in their gamer days. Government mistook Sunny to be the Data Source hacker and so captured her instead.
-Sunny feels a little resentment against Yoona for leaving her in the lurch like that, and for her currently being under the government's thumb.
-Yuri witnessed Yoona merging, started seeking Data Source for power, (to gain YN and TY's powers of summoning things from it) puts a strain on their friendship when Yoona finds out Yuri knew all along
-Sooyoung took Yoona under her wing for a while before the ship, teaching her partner-care skills. Her loyalty is put to the test when confronted with the fact that Yoona is partially to blame for her father's current situation. (Doesn't waver for a moment at the time, but little moments of bitterness pop up from time to time)
-Jessica is the first to be aware of Yoona's powers when they encounter each other in the Source, (Jessica during a mind meld and Yoona in merged form)
-Biggest source of conflict with the government as the institution becomes more and more eager to exploit the Data Source, at any cost
-Yoona becoming the official interface gives her insight into Tiffany, as both of them fear their final forms and the "death" that will follow.
Yuri:
-Being the "open mole" is a little off-putting to the other girls for how eagerly Yuri is befriending them.
-Yuri often serves as inspiration for Sunny's strategems, because she always innovates ways to combine their powers to accomplish something unique. (Sunny is just better at fleshing out the executions and details) Her tendency to focus on that kind of teamwork also leads to Sunny feeling that the team could do anything they put their minds to, including taking on the government, spurring Sunny to start breaking her own ties
-Taeyeon is both annoyed by and envious of how Yuri appears to have little angst over some of the more questionable things she's done as a part of the league, but learns from Yuri's forward-moving attitude that acceptance and moving on isn't the same as forgetting the past.
OT9 (not necessarily in chronological order)
-They discover a planet where the powers of magical girls there are magic and technology are intertwined. (Magical Girl Lyrical Nanoha)Watching the magical girls there, they notice that Tiffany is showing a longing for flying. (Not in a cockpit, but bodily flying) Previously during a hell mission Tiffany had manifested wings in desperation to save everyone, so Yoona wonders why she doesn't fly using those. Tiffany confides in Sooyoung that those wings signify her final form, which just precedes death, so she fears those wings. (Taeyeon already knew, from before the ship) Sunny has the idea from the planet to create their own technology to bodily fly. ALl of the girls pitch in to develop the technology, and they present it to Tiffany on her birthday.
-Miss A, a squad composed of the most promising journeymen from Hyo's society, are dispatched to learn about the world before their final initiation. They encounter Hyo, and inadvertently rub in her face how much more they've been able to train in pure weaponless hand-to-hand, and thus have nearly outclassed her. They challenge her to a friendly fight. Dance Line step up to be her squad for the challenge, and train extremely hard to match those who have been raised in the society. They beat Miss A because they have better teamwork, having fought together for much longer, and also because they fight extremely dirty. XD (Sunny could have fought with a hand-to-hand master at the helm of her body implants, but refuses to, both because it would be too suspicious for her suddenly to fight so well, and to hide some of Hyo's abilities and strategies from the government.)
-They end up in a mission very similar to the hell-mission Jessica was in, which disrupts her piloting abilities, both controlled (too many flashbacks) and emotional, (she overcompensates on shutting down on pesky emotions) leading to Jessica, Taeyeon, Sunny, and Tiffany being captured. The rest of the girls (all of the long-term SM trainees) go on a wild trip across galaxies to round of Jessica's old squad to help break her out of her funk. (Also an excuse to cameo TVXQ and Suju boys and the girls' dynamics with them, since Jessica's old squad have since been working with new teams)
-The others jokingly appoint Taeyeon team leader. (everyone refuses to lead and use age as an excuse to foist the position on her) She has to deal with learning to lead unconventionally (not like a red ranger) a group of alpha-types who might not need that much actual leadership in the field. The responsibility also makes her feel obligated to take care of the others outside of missions, instead of completely withdrawing like her instincts say
-The tournament "filler" arc: towards the tail end of the series, where most secrets are out, and the team is less satisfied with the government. After a remote-planet mission goes wrong and the ship is damaged, the government is feeling stingy and insists that they pay for their own repairs. They decide to win the needed parts and tools at an underground tournament, now full of rebels they pissed off during the mission. The team has to witness the long-term aftermath of a mission for the first time, including a meeting of the pirates they had humiliated before, now extra bitter and violent because of their encounter. (Except for one who went straight because of the encounter, showing how their actions can also do good.) They also witness how the local government often takes advantage of how the team curb-stomps enemies to become corrupt with their heightened power. Conflict between the girls about whether they should help, the importance of staying incognito and hiding some of their powers from the government, and now knowing that they need to be more careful about what missions they execute and how they execute them. Also, excuse for lots of awesome tournament fights highlighting the girls each having to face some part of their powers they were antsy about: Sooyoung discovers that partner tamers are now starting to use lifeforms in tournament battles, while Yoona decides to fight in merged form in doubles duels with Yuri instead of with Sooyoung. Hyo and Seo refuse to participate in the tournament, causing some friction, but become enbroiled in preventing rebels from assassinating or sabotaging the girls outside of arena fights. Taeyeon is tempted to let BoA handle most of the fighting, as she's become tired of combat. Tiffany is forced to use her former-teammates' powers. Jessica wins by interfacing with and taking over her opponent's equipment. Sunny is forced to reveal her body implants to the girls when the governemnt refuses to provide a Driver, and Hyo has to Drive her for one fight.
Elaborated stand-alone episodes and moments (not necessarily in chronological order)
-Mix of two classic episode types: the visit to a medieval planet, and the body switch. Hyo and Seo end up body-swapped on said planet, forcing Hyo to fight with weapons, (or not, initially) and Seo manifests ki-powers in a quite different form due to her calmer temperament. (much more similar to how ki powers are traditionally manifested by those in Hyo's society, achieved through meditation, etc.) Seo gets captured due to the obligatory fear-of-the-supernatural-in-primitive-cultures, and Hyo orchestrates a Big Damn Heroes moment. (later repercussion is discovering how Hyo's wilder ki powers differ from the norm)
-Out of boredom, one day the girls decide to let themselves be captured by some amateur pirates, and then semi-competing to fight their way out non-lethally. Involves a scene where the idiot pirates leave them all tied up in the same room, and everyone escapes their bonds through various methods. (Taeyeon, Jessica has a hidden knife in her boot, Sunny uses the edge of the door as a file, Tiffany summons a light shiv, Hyoyeon, Yuri, Yoona, and Seohyun contort out, and Sooyoung uses her Ghost beast.) Lots and lots of banter and snark about all of the amateur mistakes the pirates make.
-Amber and Krystal join the positive League circuit, which gets Jessica and Tiffany pissed off at Yuri for helping their league careers instead of discouraging them from the life. XD
-Taeyeon gets the body/personality-split episode, dividing into the dork, the leader, the power ranger, and the pervertromantic/suppressed feelings. Extra complications ensue when Boa also splits out. Oddly enough, Boa is more stable split out than when she possesses Taeyeon, as those times she's just desperate and slightly crazy from being suppressed by Taeyeon for so long. Forces Taeyeon to confront Boa, and the others to deal with her other aspects no longer balanced by each other, and bringing Taeyeon's emotion-bottling problem to the fore.
-The space-western episode: wanted outlaw trio Rino, Maryss, and Jaewon manage to own the girls, despite their best efforts.
-Comedic deconstruction of she-fu: Yuri spars with Tiffany. Involves one moment where Tiffany pulls a twist layout with her katana, a move she had previously used effectively against enemies. But Yuri, having fought against acrobats before, simply stays grounded, blocks the slash, before twisting and roundhouse kicking Tiffany in the gut as she nearly completes the layout. Later, there's an inversion when Yuri attempts a leg sweep on the landing on one of Tiffany's evasive flips, but Tiffany does a leap out of the landing, getting in a jumpkick in the process. The she-fu is only effective when not used/timed predictably, and not using any common sequences.
-A mission involves all girls who have flying capacities to do so and lie in wait in the sky. They bond over how awesome flying and aerial battle is. Grounded members express envy or I Don't Get It feelings.
-Running gag of Yuri proposing a solution to a problem based on passing knowledge she has on it, but Sunny upstaging her because she mentally contacts an expert on the subject. Include in conjunction with IY shout-outs, especially a catching-space-chickens mission.
-At some point they land on a planet where ki-powers are tapped into elemental control, (ATLA crossover :D) and Hyo temporarily gains wind powers. Seo gets her hands on element-affinity blades. Shenanigans ensue wherein the planet's people are engaged in some highly complex political games and SNSD's presence throws a giant wrench into every one of them.
-Running gag that when they encounter minions to be vanquished, they begin exclaiming how ugly the things are and how pretty they themselves are in comparison. They begin vanquishing them in increasing creative ways out of boredom, like with the pirates. Becomes a competition where quantity, quality/creativity, and difficulty are the categories for which they receive scores.
-The heist episode actually turns into a prison escape crossover with Running Man. :3
-Running gag that because hand-to-hand is still useful, a lot of fighters end up seeking out Hyo's society for training, and she's made friends with most of them, (shout-out to her real-life extensive network) so nearly every "guest star" that shows up, are friendly to Hyo while only knowing Yuri as an opponent in the leagues. Yuri makes a crack at some point that Seo's not the same because training non-energy weapons isn't as useful. Then she wonders why Hyo didn't meet her when she went, and Hyo says that she knew when Yuri came to the planet, but chose not to meet her becauase she didn't like her at the time. ZING.
Potential end-game: two types of "series endings."
Type one is them simply gaining enough leverage over the government to negotiate a better deal, where they have more autonomy and wiggle room in how they act, but still are under the government as important assets. Think SG-1. This preserves more of the episodic status quo, with a "and so they continued on..." type of ending.
Type two resolves all status quo storylines and is a definite ending to their space-faring and doing missions together under the government. Either they get enough leverage to retire from the government and settle down as they please, or they end up starting a full-on rebellion against government supremacy, like Firefly's Browncoats.