Messing with maps...

I can probably shed some clarity onto this. Maps are made up of a few different things that are all controlled by 33 bytes of map info that's been pretty well documented. You can find that information here (http://www.rpglegion.com/ff6/hack/ff3info.txt) in the "Location Properties" section.

Every map has 4 tile sets (plus an animated tile set), and 3 layers of map data although most don't have any layer 3 map data, and all that is decided by the location properties. So the maps you see with gobbledygook in them are just maps that multiple sets of location properties point to with different tile sets. You can edit those, but erasing one will erase a several locations, so careful with those. Best to wipe town maps since those are generally single use.

As for the space the maps take up that's pretty tricky. The map data is compressed using a type of LZS compression. In practical terms what that means is that maps are stored in horizontal wrapping rows (world maps are vertical) starting in the northeast corner and repeating patterns are reused. So if you have a row of 8 of the same tile, it only takes 3 bytes (I think) to store, but if you slap a different tile in the middle, then you've got to use 8 bytes (well, 7 I guess). Both FF3LE and my old map editor have compression routines to recompress map data when you save it, but there's an awfully good chance your map is going to be larger than the previous map if you're not careful about using repeating horizontal patterns.

The good new is that the pointer point to the map data (which you can track down through the location properties) are absolute long pointers so with a bit of work you can relocate your map data anywhere in the ROM or expand the ROM and open up a ton of space for maps.

I think it'd be possible for someone with more ASM skills than me to expand the number of maps, but it wouldn't be super easy. I don't know the code that loads the maps, but I know the data and there's definitely room for another bit so expanding out to 767 maps should be doable. Probably best just to relocated and wipe unused maps though.