@Based99 it all just depends on how Aizen!reader would exist morally. Is he just good? Neutral? evil? sounds like you're going the relatively good route though.
Team-wise, if you're gonna do momo, it's probably easier to drop tosen, but like... the trio aura farm of aizen, gin and tosen would be kinda lost. Why not like, captains, like byakuya(yes ik ironic considering my pfp), i feel like the dynamic would be funny, and someone who's kinda a wild card? Idk, never let me cook. I need that gin x rangiku tho.
Also, im pretty the 2 males 1 female thing was kinda just a popular trope during the 2000's, harry potter, atla stuff like that, it's not a strict rule in naruto since there's other teams(that have absolutely 0 screentime) with all girls or all boys, especially later, during shippuden and things like that.
I wonder how your take on Kyoka suigetsu would work, due to genjutsu needing mediums and things like that. Sword or the aizen water theory, or something totally out of the box. And how your takes on Aizen's overall intellect and , lets say, horrible relationships with corrupt systems would be. I know whatever you do, it's gonna be peak