Do you think that you could do texturable environment ?
Like, for example, 5 basic textures (concrete, grass, snow, red wall, greys wall) that mod makers can add to an object by calling the texture through a number (idk how its works, but something like Text : 2).
And maybe a way to add more textures to make possibilities endless (sorry if you already discuss that, there are too many pages to read ^^).