Doing it for the fun of it is cool, but are you saying there SHOULDN'T be a reward for getting all of them? Every game I can think of from the top of my head rewards you for collecting all of the "things". Making an interesting unlockable at higher than 100 emblems doesnt force anyone to get 100 emblems. What the heck makes you think 100% would be forced? If an interesting unlockable is at 200 is it forced? NOOOOO ITS NOT. If it's a character, i wouldn't call it forced but it'd be a damn good reward for the people who actually did 100% it, but its highly unlikely and no, i'm not asking for a character as a reward (if i did, it would be big the cat, since i view him sort of like an easter egg, possibly due to him being an april fools joke)
Hyper Sonic has always been a part of SRB2, and it being an easter egg for 200 emblems would be a neat enough reward. But it doesnt force anyone to collect 200 emblems. It's not like it's a new character, Hyper Sonic would probably be just like Super Sonic but armageddon thok and cant drown. Hyper Knuckles has never been a thing in the past of SRB2 but if they include Hyper Sonic it would only make sense to include Knuckles i'd think.
Again, I dont think hyper is really that good enough to where 200 emblems to unlock is really a bad thing. And no matter what the reward is for 200 emblems, I don't think you would be forced to 100% the game and get all the emblems. You can easily just not get that unlockable. Coming from someone who has gotten all 200 emblems, I dont think i'm very good at srb2, so i don't think its very hard to get all 200 emblems, and i cant say emblem hunting made me better at the game, though it might have.