Thank you very much for the reply. I'm even more psyched(?) for it now.
As to what people might expect considering the list of features that you named, well...
Breast expansion(BE) usually(but not always) has some connotations to it, like lactation (and breast preg for the really hardcore preg fans).
Multiple simultaneous pregnancies are pretty popular(at least on the discord that I'm part of). It's up to you if you want to expand(hehe) it further to outright hyperpreg.
Futa can be hit or miss. In this case, I'd want to know what the protagonist would use it for, and again, there are some pretty out there fetishes when combining futa and preg.
All that is just my take though, so I might be wrong on every front.