Hence why turning him into an adult is a bad idea.
He should be able to enjoy the free country post final war as a child.
Yeah I forgot to throw in, it would be extremely plot convenient (but it's not like Oda is a "stranger to that" ofc), but I have the funny feeling, Momo will get aged up BUT Bonney will appear one way or another, she will meet him at some point and she can deage him back to childhood.
But this might be Momonosuke's tragic sacrifice and character development too. His sister was already forced to miss out on her childhood in her own way and grow up prematurely too. At least she's still alive though for now and they can finally reunite and celebrate avenging their parents, country and themselves even.
It's actually INSANE that they've not even met and thus reunited since Momo was sent forwards in time to current day! Hiyori has been weirdly and unnecessarily irrelevant this whole arc, when her brother was getting kidnapped, beaten, tortured and almost executed!
Where rhe hell is she and what is she doing?! Same with the Ame No Habakiri! Just what are you playing at Oda? And why make us think she was there healing the Scababrds or that it was Toki? He even had the nerve to make it seem like Oden had "come back to life" and give us the most extreme death fakeout so far!
I agree though, I think Momo should get to remain a child but I have a bad feeling Oda will age him up at least temporarily for the sake of an emotional, harrowing narrative and the consequences of war and such. I really hope if it does happen, that Bonney will deage Momo by some opportunity. I've actually beern wishing they could reunite with their parents in living too somehow, as in their parents wouldn't be dead or would be resurrected somehow or at least they would meet their ghosts or visages or something like that.