I'm kind of against both of these suggestions. Allowing speed gains when running down slopes means that there has to be a dynamic running speed cap, which would as a side effect also allow Sonic to keep his 60 FRACUNIT thokspeed when on the ground. That honestly sounds really fun but it would also completely change the way we play SRB2—which I guess with 2.2 changing most of the game's design anyway, is not a huge deal, except that we already have spinning as an effective and sensical method of doing the same thing, not to mention it might alienate veteran players and make Sonic even more overpowered (because some people seem to get butthurt over that). The hold-spin-to-land-in-roll mechanic seems less intrusive to me, but when playing classic.wad there have been a lot of moments where I accidentally performed the move when I didn't want to. That might just be me not being used to the mechanic, though I definitely felt extremely frustrated whenever it happened—not to mention that it happened more than I found deliberately performing the move to be useful (once again however, 2.2's new slopes may possibly flip that ratio, as has been mentioned). It also inadvertently buffs Sonic because he can roll on the ground at the speed of his thok much more easily after landing (you can perform this in the current game but it requires some precise timing). More than anything I just don't really see why having to press the button after you land instead of being able to hold it down beforehand makes such a big difference; the only case where I can see it being more useful is to protect against enemies when landing. That's my two cents on those things, I guess.