Sonic mania plus added two amazing new characters, but no Amy Rose, even after fan outcry and her featuring in Sonic CD, one of the original sonic the hedgehog games.

She recently started in a sixth part of the 'sonic mania adventures' youtube series, (made by SEGA and others that worked on sonic mania) and it showed her to have a unique moveset that could be put into the games, such as a hammer swipe and hammer drop th harm enemies.

Amy has been in several sonic fan games and has worked quite well, and some of those assets could be put in sonic mania.

Finally, Amy would be the first female character added to the game making it seem more gender diverse and female friendly.