I'd like to see sections that use similar gimmicks as the prior zones, but re-imagined in a space station. Low gravity, sections with no air, occasional gravity flips, lasers, etc. Basically, a final gauntlet composed of everything the game has thrown at you so far, but more over the top. Not necessarily in difficulty, but definitely in presentation. It should make use of prior level gimmicks like underwater sections and gargoyle puzzles, purple goop, lava, etc. At the same time though, it should do this all in a way that feels unique from the prior zones so as to have it's own identity. A combination of everything you've learned up to this point, but now you have to learn to pass through in a new way.
I can imagine for example a room with a gravity flip in the horizontal middle and low gravity everywhere else with purple goop that bounces you back the other way on both the ceiling and floor, and a series of platforms you need to jump across to get through the room. Some of the platforms are out of Sonic's reach, forcing him to make use of the goop to progress. Not necessarily dangerous, but forces you to think about using old gimmicks in a new way. Perhaps follow this up with another similar room, except now there's lasers you have to carefully avoid or there's no air so you have to get through on a time limit, etc.