This mod is really awesome!
I have a suggestion for the map system though. Maybe you can include the option for an "area" map that hides sections of the entire map until you've collected the map item for a certain area. If you don't have an area's map yet, it can still show only the screens you've already visited, and also the screens that contain the map items (so that you have an idea of where to go).
EDIT: I spent some time in the Editor and found out a way to do this, though it does take a while to set up, so maybe having a different way to do it would be better.
Here is my demonstration level. This way uses Flags, Shifts, Warps, Signs, and Map Spoofing. Because there are only 10 Flags (well, 10 that I'm aware of anyway) that means you can only have up to 10 Areas. I'm still a bit rusty with the KS engine in general so there's probably a more simple way to do this. Also, this can be broken a little with the umbrella or double jump by collecting the map powerups without touching the ground square its standing on.