So, regardless of what you might personally think about Sonic Forces, one part that I think the majority of us can agree on is that the customisation of your avatar was awesome, by far my favourite mechanic in the game. I loved the variety of options available for species and clothing styles, and the reward system the game had for these items, gifting you more cool stuff for your avatar for completing challenges in the game. Personally I would really like to see the customisation elements from Sonic Forces return in future Sonic games.
There's just so much that could be done with it. If it gets released on the same platforms, we could be given options to import our previous characters from Forces. This could even play into the medal system they had going, for example they could double the amount of total medals to earn for your character, which means if you import a fully leveled character from Forces you could have the advantage of already being halfway there, and it would make medal grinding less of an issue. Not to mention expansion and improvements to the system, like more species, extra voices and hairstyles, perhaps a better way of classing customisation so that the same outfit doesn't have 3 slots just because of the different colors. Heck, give us our own color schemes to use in a spectrum paint tool style, and while we're at it, decals and tattoo like options, I could go on, and this is to improve a system that's already really great. I wouldn't be mad if they made it just the same, but I would be a little disappointed.
But then there's the issue of game play, and story problems. Not everyone likes the Avatar style of play, or the idea of Wispons. I was fine with it myself but it did feel a little too similar to Modern Sonic at points. How would you change or add things to make the Avatar game play more appealing? As for the story, well that's kind of difficult, if you consider the note that Sonic Forces left on, I'm not really sure what could be done there. Maybe the avatar can have a spin off story, separate from Sonic's own, but linked in to a final boss encounter like the Adventure games did? Or even just give the avatar their own separate game, but after Shadow the Hedgehog came out, I doubt that's gonna happen.
Then you also have the problem of the time frame. How long should there be before the avatar could return? Should it be in the very next game, or should we maybe wait for more titles to pass by first. After all, we don't want the Avatar to end up like Classic Sonic is in the modern games: Overused, unnecessary and redundant.