Hmm..interesting topic...
Well, I would want for Modern Sonic's BOOST controls to not be as easy to fill. Have it fill up a lot less when you defeat enemies and what not.
As for music; I don't think there's..oh wait, I would have Hydrocity Zone Act 2 in place of Act 1...yeah.
I would like Route 99 as an additional level, but I feel it is better siuted to the 3DS version...which let's face it, ain't getting anything new for the forseeable future.
DLC such as Egg Fleet or Starlight Carnival would be nice too...
Also, make the bosses a bit tougher? Hard mode adise, four hits is really cheap to me personaly when you're up against a gigantic robot crafted after an fat scientist and sadisitic and powerful beast called the god of destruction/chaos in a liquid state...
That's all from me for now.
