If anyone’s interested in a similar mod for Sonic Mania, here’s are some links to Amy XL:
Sonic Mania Plus ver.: [NSFW] Amy Mania XL Plus [Sonic Mania] [Mods]
Sonic Mania vanilla: Amy Non Plus by Eishiban on DeviantArt
It doesn’t feature weight gain like the hack of sonic 2 does (just one static size), but it is very well done.