>>58119969
>I heard that Blazing Emerald removed the option of playing as May because to make more room for other stuff, then it became nearly impossible to add her back.
May doesn't take that much rom space so that's almost certainly not the actual reason for her removal. The blazing emerald v1.6 rom also uses only around 2/3 of the available space.

>Lastly I heard that in Pokemon Elysium you need two different roms or some shit like that because the game is so big, haven't looked into that one yet though.
That was due to dev incompetence instead of rom size. pic related.