Why Momo Can't Learn Bankai?
When reading fanfics about Hinamori Momo, one of the subjects that comes up is the fact that the writer wants the fukutaicho of the fifth division to become stronger then she already is. It is overlooked that her personality is a rather mild one and that she is shy when speaking with others. This comes into play with the fact that she can't learn Bankai as she is, yet some writers just give it to her.
One of the arguments they make for her learning Bankai happens to be the fact that she is a fukutaicho of the Gotei Thirteen, so that must mean that she is of a high enough level to learn Bankai. However, there are only two people of lieutenant class who have in fact achieved this attack. That would be Abarai Renji and Madarame Ikkaku.
Momo on the other hand is in the lower power levels of the fukutaicho. Whether or not she should in fact be a fukutaicho is brought into question due to the fact that Aizen selected her specifically because he could easily manipulate her, not necessarily because he saw her as of lieutenant quality material. With this, the questioning of whether or not she deserves the rank for her division is asked.
This doesn't mean she doesn't deserve the rank though. It is just that, unlike the other two that Aizen hand picked, or four if you include Hisagi, she has yet to prove her worth after the time that her taicho betrayed soul society. Even Izuru Kira stepped up to the plate and proved that while he had a rather nervous personality, he could fight on his own.
Momo was stuck in a coma for a long period of time, her state of mind still being brought into question. I've seen some fanfics that think that this was the opportune time for her to learn Bankai as she had plenty of a chance to speak with her zampaktuo. However, they forget what is needed to achieve this skill level.
To quote the Bleach Wiki at this point in time, “to achieve Bankai, one must be able to materialize and subjugate their Zankakuto spirit. Materialization means the opposite of getting dragged into the Zanpakuto's inner world. Instead, the wielder needs to summon the Zanpakuto's spirit into the pysical world.”
It other words, it is impossible for her to learn Bankai while in her inner world, which is where she would have been while in her coma. Yet I've seen quite a few fanfics that have her coming out of her coma to instantly learn or have Bankai. The reason they do this is because they want their favorite character to be even cooler then before.
Personally, I think Hinamori Momo is all right just the way she is. I don't think that it is really matters if she isn't the strongest Shinigami out there. She simply has to be her self and I like her for her normally meek personality that sometimes develops a flair of attitude when her temper erupts. Unless Tite Kubo does it or a fanfic writer gives her proper character development, I don't see her achieving it.
The first thing that has to be achieved for Momo to eventually learn Bankai is for her to get over her mental problems. These kind of things in fact take time. She has to still deal with the fact that Aizen betrayed her. She also has to deal with the fact that the child who grew up beside her stabbed her through the chest.
The second thing she has to do is physically get stronger. To quote the Bleach Wiki again, “only the strongest Shinigami can use it.” Momo's abilities are below many a characters, Matsumoto Rangiku, Hisagi Shuhei and Kira Izuru... even Ise Nanao. This isn't something that just anybody can learn, only specific people can. There are so many I expect to learn Bankai before her.
Both of these things will in fact take time. There is also one other factor involved. Momo has to want to learn Bankai. If in the long run, she doesn't want it, she won't ever learn it. She is the type personality wise to follow, not to lead. That was why Aizen picked her out of a lot of other people. Her personality fit what he needed.
So, she would need to find a reason to learn Bankai. Perhaps a jealousy of Toshiro would be enough, but the fact is, there was plenty to be jealous of long before this, yet she didn't act upon those feelings to become stronger. Or maybe the feeling of being inadequate will be a reason for her to learn the technique. But truth is, that is a sign of weakness, not strength.
So, unless Tite Kubo makes her have a Bankai or your willing and able to go through the character development needed, don't give Momo the ability. Sure, it might be cool for her to have this ability, and for her to be a captain of the Gotei Thirteen, but this is completely unrealistic. And Toshiro/Momo fans... she does not have to have Bankai or be a taicho to be his perfect soul mate.