Well, a fully SEGA focused game brings more fandoms together like Smash does, and crossovers are the only hope fans of many old series have of seeing those characters in anything modern again... plus, I’d imagine some people are somewhat turned away from the idea of a Sonic focused game after Team Sonic Racing was basically a Sonic only sequel to the All-Stars Racing series but didn’t even do the Sonic focus properly (15 characters just isn’t enough, especially in a modern kart racing game. MK8DX has like 42 characters and CTR:NF has 50 characters right now with more to come.)
If there were to be a new Sonic only fighting game, I wonder how they could utilize the unique speed focus that Sonic characters in general have in order to make a very unique feeling game (and without just making everyone be super hit-and-run focused like Sonic in Smash is.) Like, I wonder how stuff like slope physics, half pipes, ect. could work in a platform fighting game? It’d be kind of casual focused then, but it’d be really interesting to experiment with.