That's a good idea, but for a WAD. SRB2's point is to capture the essence of Classic Sonic's era, platforming, mind-bending speed, FUN. The survivavility mode would fit more in games like CoD, DOOM, and that kind of shooters. Chaos mode was truly fun (at least for me) but it was cut from the game because... I dont know, peanuts?
Either way, it's still a fun idea.
Either way, it's still a fun idea.