I know a lot of people thought of many different ways to bring back maps, and yes I know a lot of people are sick of it, but I got an idea in mind lately, not sure if it could work but it's worth a shot.
You guys know how we convert models to work in the game right? Converting them as .dts for add-on models, or .blb for bricks, but what if we create a new file, or Badspot if he ever gets interested, something like .map, basicly there could be a little executable program with a little menu, that allows to import .dts files and export them as .map files, that gets in a folder in the game that opens in some sort of new Terrain Editor that allows you to resize the models, position them properly in place, let's just say you made a terrain model, and the buildings that goes with it are separated, and then you can position everything in place, and save it as a new map, with proper collisions too that are generated after saving the map, or entering a test mode with your character.
The Terrain Editor could allow players to add ambient lights, effects and particles (like smoke, river, other things) and props that could come with it.