MM2AIR
You know those Goblin actors that can be seen when going up the side stairs in the square sections? How about getting the impassable lines out of the way so that people can platform their way to the side? It's annoying enough having to watch out for pits, then there's homing weapons in the map, too. I don't know about everyone else, but I'd like another way out of the square sections from which I can see what awaits me instead being of paranoid of an Air Shooter to the face when going up the stairs to the middle.
MM7DW3
Actually, the map is pretty good. One of my favorites, in fact. Although ever since v2a was released, I've been thinking that the large, open area with Rolling Cutter and Freeze Cracker (Is it? Forgot the other one...) could use some cover. Maybe a pillar in the middle between them, or one for each. That would also give Rolling Cutter places to bounce off from.
MM4BRI
Just remembered this one. Because of all the jumping here, fighting is kinda difficult. Since this is pretty much all of the stage, expanding the size of the large steps might not be such a bad idea. Otherwise, just place run-by steps in their middles and/or sides for easier travel. Scorch Wheel is an excellent offensive weapon here, but the jumping hampers the speed boost.
I think I had others, but that should be it for now.