I think Sonic should be very mobility focused. As it stands, Pikachu, Fox and even Wario may not be faster then him, but they are all characters who have answers and approaches to high level play tactics. Sonic's priority is also just an inherent problem in his moveset, but I think it can be solved.
Since Sonic is lacking in priority, I think he'd definitely be the character suited to make use of some invincibility frames. Extended invincibility on his side-B would let him get through projectile walls while still being foreseeable and punished. The canon S3K nair can also be useful for clutch approaches or openings.
While the instant homing attack still has horrible priority and has relatively weak reward, the fact that its instant, returns Sonic to the ground, and cancels into Side-B/Down-B (Which of course cancels into another jump or shield) gives Sonic great maneuverability that is super flashy, fun to use, and I think will be a good asset giving Sonic players the spacing tools they need. Combined with the spinjump hitboxes now coming out frame 1 and he can start to punish people for getting too complacent.
With the big things out of the way, making sure Sonic's moveset makes sense along with fitting his playstyle becomes a new affair. I really like the spiking Usmash as an anti-air reward that doesn't always get guaranteed kills, but can lead to one on techchase. Its slow start-up and lengthy animation will keep it from being abusable. I do feel Sonic's grabs can all yield a reward of some sort. Bthrow and Fthrow should of course be good for getting them off the stage, with Bthrow killing at appropriate percentages. Uthrow can already kill an opponent without DI, since no DI lets you follow-up with Uair. The Dthrow speed-up that let Sonic punish techers was an obvious solution.
Kill moves; for a move he can techchase and kill with after spiking Usmash we have a few choices. The center of Nair's first hitbox would be fine without being a great buff on its own considering its range. I think if we decided to speed up Dsmash for this purpose I'd want to tone down its power so it doesn't overshadow Fsmash for every situation. Another dream of mine was to add a sweetspot to his ftilt, seeing as how Ftilt hardly has any pros over dtilt which comes out at the same speed. Its only advantage over it would be its range, which would make it an ideal move for a killing or low angle sweetspot. Some other good candidates for speed-ups (Besides the spiking Usmash and maybe Dsmash) would be his Utilt and Bair.
His off-stage game can be accentuated a bit. If the HA was strengthened it'd be a decent combo ender and edgeguard that looks nice too. I was also thinking of giving his Dair IASA frames allowing him to use his Dair spike on recoveries that are too telegraphed or predictable without Sonic dying.
Feel free to keep posting ideas and we can eventually get a good summary and a pac to test going. I think terms like rushdown/pressure and bait/punish are far too broad and vague to characterize an entire moveset. These are things all characters do, just interchangeably for different situations. In my opinion, Sonic should be able to move and space precisely in the hands of a good player, and haphazardly scary to the opponent. His punishment should be moderate, in exchange for being fairly safe himself and having good recovery. Of course theres much more to him, but overall Sonic players should be on their toes, have a great and constant sense of spacing, and control the flow of the match through educated capitalizing on openings, punishing overagressive players, elaborate and tricky setups, and locking the opponent in more complicated games of footsie then Falcon ever can with his lingering dash dancing.
Sonic wasn't as bad as Ness in vbrawl. He was higher tiered, wasn't he?
Anyway, I'm not gonna talk about Ness in here.
I'm not sure many Sonic mains really agree'd with his tier placing... But besides that, its a whole different game now.
. 
