I'd been meaning to write this up since the finale 3 months ago (can you believe that?!) and with everyone unable to contain themselves about S10 (especially on TWITTER making it near impossible to stay spoiler free :sad:) I've taken to writing this while ignoring most of what I've had spoiled about S10. In no particular order:
Chloe. We all know by now that Allison Mack's run as the only cast member other than Tom Welling to be in every episode of Smallville is coming to an end in the final season. It's disappointing to hear, and while I hope that she is in as many episodes as possible I think everyone needs to calm down about how many episodes a character is in. Every season we go through this with Lois or Oliver and I can't think of another TV show where their presence in every episode is demanded of (Then again there is also the point that with such a small cast, it should be possible to include every character in every episode). From everything around the show it sounds like they want to give Chloe the ending she deserves so it doesn't sound like they'd kill her or anything to fit into this imaginary continuity people seem to think every iteration of Superman has to fit together in. While my hope that they would convince Allison to be in every episode didn't come to pass, now my sincere hope is that she is in the final episode (would be nice to have her in #200) and maybe even in the final scene of the series. If they had decided that Chloe needed to go away, i was thinking something that would be true to her new direction as a character and in showing her affection and knack for protecting Clark would be that she would replace Martha Kent as the Red Queen.
Diversified Cast. One thing I've disliked as Smallville has continued on is the decreasing size of the cast and the disappearance of the different age groups involved. In the early seasons you had three groups: the Adults (Kents, Lionel Luthor, Gabe Sullivan, Nell Potter, various teachers/sheriffs), the young Adults (Lex Luthor, Helen Bryce, Jason Teague) and the kids (Clark and the gang). Now in the later seasons we basically have Clark and the gang as young adults. No one older, no one younger. Season nine gave me some ideas that I'd love to see explored with a new young bunch (Mia, Zan & Jayna, Courtney) along with the older bunch (Carter Hall, John Jones, Perry White, Martha Kent) - it reminded me of the good old days and I'd like to see it more in S10. Having Clark and friends act as mentors as well as have those they can look to as well.
Guest star arcs. With Chloe's reduced role, I'd rather see the episodes she'd normally be used in go to other guest stars for their own little 3-4 episode arcs instead of just a one episode shot (or something ridiculous like the S9 finale cameos for all those characters) Like John Jones, Mia, and having a story arc that helps round out their character and their relationships with the main cast that can't fully be explored in one episode.
More inter-connectivity. Another thing that has faded away over the seasons is how the characters of the show used to interact a lot more with each other without needing Clark to be there. Now it seems you only see a character when it pertains to something Clark outside of the rare episode where the character is the spotlight. As a result we saw a lot less of Chloe/Lois cousin action that was so prevalent in S4&5, Lois has more interaction with the villain of the week than Oliver and before the start of Chlollie we only saw Chloe in the watchtower talking to Clark about his rescue duty. I miss when Lex would visit the Kents or Lana at the Talon, or Chloe/Lana visiting the Luthor mansion and Clark would not have to be involved for those scenes to happen.
Return to Red & Blue. As nice as it was for Clark to be wearing the House of El crest in season 9, it came at the suffering of his color scheme which went dreadfully gray and dark. The look of Smallville for many seasons was Clark in the red/blue jacket/shirt combination and when Season 8 brought the Red, Blue Blur it was the most brilliant innovation to the mythos and I hope it returns in S10. I can understand the wardrobe change for Clark now that he's in the Daily Planet but maybe some time in the red & blue is overdue.
Cast reunion/retrospective for DVD. This is more something I'd like to see in the season 10 DVD where they would get every main cast member over the 10 seasons (anyone that was in the intro) and put them in a seated room environment ala the Survivor/Reality Show reunions and have them reminisce over the seasons. Perhaps as moderators you could have Gough, Millar, Souders and Peterson. Talking about memories, first impressions, their last scenes, funny moments, the fans, what they wish could have been done for their character. (Also bring back the gag reels!)
Cless. Now we head into the more unlikely wishes to be granted. This one would be having Clark and Tess together, either under a spell or brought together due to the situatons. Unfortunately after S9 basically put the Clark/Lois relationship on fast forward (compared to S8), that pretty much knocked the possibility of Cless out of the waters. I remember seeing 'Turbulence' in S8 and thinking that now that Tess knows about Clark that it would be interesting if they got together and had a relationship he never could have with Lex no matter how hard they tried. Instead Tess was handled terribly in S9, had scenes with Zod and Oliver for the most part and only saw Clark when he was throwing her around. I was so disappointed.
Bruce Wayne/Graysons. I think everyone remembered when Adam Knight appeared in S3 for an extended stay and speculation was that he was Bruce Wayne in disguise. Unfortunately that wasn't true and the character took a much darker turn. Now going into the final season of Smallville it's clear that WB/DC has a problem with the idea of Bruce Wayne being portrayed on TV. I have a feeling they're trying to keep it a movie property in the way that they only turned to TV for Superman after the movies started to wane in quality (after Superman IV came the Superboy TV series, Lois & Clark and now Smallville). That said, I would love it if they referred to Bruce Wayne and Gotham in passing, like if Oliver or Tess came from a Wayne function in Gotham, or the newspaper had some article on the return of Bruce Wayne. Also with how CW teased about a Graysons pilot, how about instead having the circus coming to Metropolis and Clark seeing the young acrobat couple, The Flying Graysons. I'd settle for that too.
Wonder Woman. This is the other DC character that fans have been clamoring for to make an appearance in Smallville, and while it probably won't happen either I definitely would like to see the Smallville interpretation of the character. I think they would focus on the Amazon aspect and have her be a warrior very connected to nature and the wild (except of course with her silver bracelets). Of course it would work better with the S8 Clark/Lois status quo in that they liked each other but were free to be mixed up with others.
Directing. Lastly, I know that Smallville has the trend of giving its main actors the opportunity to direct an episode in the season. What I'd love to see for the final season is that they let all of the actors who have ever directed an episode of the series to direct an episode in S10 (John Schneider, Michael Rosenbaum, Allison Mack, Tom Welling). I'm sure we'll see at least Tom direct one.