This is something I'd love to see changed if a remake ever got made. Keep the option for the old, inferior controls for those who for whatever reason want it, but allow these abilities to all be mapped to different buttons for ease of use. I can't even count the number of times I've died because I wanted to light speed dash over a bottomless pit through a trail of rings, only to do the wrong action and fall to my doom.
I have. If you couldn't beat Final Chase, you probably would have a hard time with Cannons Core. The final story's actual story I'd say is worth it if you care about it, but the levels themselves aren't really anything to write home about aside from the great music. If you ever do get around to it, the best advice I can give you is get the aqua necklace as Knuckles first.