Sonic's airspeed is fine. He has the 6th fastest top airspeed in the game you know <_<.
Raising Sonic's gravity would also make him easier to combo, while not really adding anything to his game (anything he would gain with more gravity can already be accomplished by fast falling).
It's his jump speed that concerns me, not his fall speed, though perhaps that could be raised as well.
If we only increase full grav and decrease dgrav accordingly, the end result will be the same fall speed, and thus the same comboability, but faster jumps. If we increase both ugrav and dgrav, then we could lower his individual hitstun to compensate.
Faster fast falls don't cut it enough imo. You can add as much fast falling speed as you want, but it won't change the fact that his jumps are floaty and take a while to reach their apex for you to be able to fast fall.
I'm just saying we should experiment once we have the tools to really play around with Sonic's physics without screwing up his UpB. And that goes to other characters as well, like Diddy.
Also, just for posterity, here are my old test results on which characters have their recoveries affected by greater ugrav:
Link (Up B does not go as far in the air)
Samus (Up B, but only in the air, as doing it on the ground makes it gain the same distance as usual)
Luigi (down B when pressed repeatedly is nerfed, on both the ground and air)
Sonic (Up B, ground and air, as we all know)
Diddy (Up B distance is nerfed, ground and air)
Sheik (slightly, as the little bit of distance you gain when first performing her Up B is reduced)
Pit (his Up B is harder to control, and cannot go up as much)
Yoshi (slightly nerfs the distance gained from his Up B, but his double jump is unaffected)
Ice Climbers (both Side B and Up B are nerfed)
Dedede (Up B is nerfed on the ground and air)
Bowser (Up B gains less upward distance)
Toon Link (Same as Link, though obviously not to the same extent)
I think Wario might also be affected, but I'm not sure.