To be honest, what would improve this would be a revision in the game mechanics to make it more playable on a basic level, and also to make it more like an average platformer.
So that'd mean removing vertical aim (aimmode 1 for all monsters and however you'd handle that for the player) and hitscans (replace them with projectiles, like Action Doom), stopping things from moving sideways so that dodging is purely a vertical thing (be sure to keep the high jump height and crouching) and making it possible to jump up on to ledges in the same fashion as Mario (ie. you can jump up onto them, but not jump down through them), which would be acheived through silent teleportation onto a platform behind the lower level one. Also making sure that monster activation is limited largely to whats on screen would help. The camera being zoomable is quite handy though, so I'd leave that.
This way you could do it properly. Stopping moving sideways would probably involve player blocking lines at the players width, and monster blocking lines wherever necessary. I know this is a lot in the way of changes, but it'd make the whole thing work better, and be easier to play.