Well, a lot of levels need complete redos, anyway. Way too much gimmicky nonsense, I've said it here and elsewhere, Sonic Team has an irrational paranoia about players' attention spans. Also, while I am in favor of proper acceleration and deceleration, I actually like the run trigger mechanic, because, like it or not, it's somewhat necessary if you want to actually regulate Sonic's speed. I'd probably make it a toggle instead, though. A manual 'gear shift' mechanic might also be an interesting idea. Though there's always the problem of controls at high speed, it's a major flaw of many 3D Sonic games and why Unleashed, Colours and Generations made him control like a bloody racecar at a certain threshold.