Got through playing this level with a few others just now, and here's what I can say about it:
As for the design itself, for the love of God, why the turrets? They're spammed everyfuckingwhere in that one room and exist to annoy the living shit out of you. And depending on what character you are, you can skip them entirely(along with the majority of the level). Keeping some turrets seems fine but at least reduce their numbers. Overall, a lot of the gimmicks used in the level were pretty unique, and I would've enjoyed them a bit more had I not been using Tails to skip the entire level.
Moving onto characters. To be very honest, I don't like the changes you made at all. The Knuckles nerf is clever but makes Knuckles entirely useless in this level since the level's design isn't modeled to reflect his change. He's pretty much reduced to a character who has a short jump and nothing more. Maybe his nerf would be useful in a Super Mario 3D World mod? I don't know, but I sure didn't find it fun. Sonic's homing thok wasn't exactly the greatest thing either. The actionspd is set really awkwardly which at some points makes you stop trusting your thok as a whole because odds are it won't get you across much of a gap. I don't like to trust my homing attack much either because odds are if I use it on or near a spring it'll fling me very far in a direction I didn't want it to. As for Tails, why on earth was his spindash removed? It breaks the pace of the level by a hell of a lot since you have to start flying from hardly any speed. I did notice his new projectile attack but I found it completely fucking useless since it's faster to either hop on top of the enemies or skip them entirely. One more thing, if you removed Tails' spindash and modified his spin ability in the first place, then why didn't you switch the god awful vanilla flying to something like holdfly with CA2_MULTIABILITY and just reduce his fly tics? Spamming the space bar made my thumb hurt.
I also noticed that you included Jasper in this level, woo go fanchars. I like the character itself, but dear God he's been suffering from the same ability nerfitis that the other characters in this level have. Cool a spark burst! Ups the range that the player can hit enemies at... at the expense of all of his momentum. I don't understand this at all, why give him a combat ability? SRB2 is a platformer. His ability should assist in how he can maneuver around the level, not some sort of mid air nuke that brings you to a screeching halt upon use. It pretty much forces him to complete all platforming in the level without assistance from an ability, basically making the player realize that if they hit jump in mid air, they WILL die. Please, at least create an ability that improves the movement of Jasper instead of giving him a pointless combat ability that only speeds up the process of killing enemies. I can not find this ability to be good for the life of me and it just stopped me from playing as Jasper entirely.
Again, I liked your gimmicks, but those character abilities are god awful. My experience with this map overall was anything but enjoyable.