Already in as a random (and likely) find in parking lots and garages, as well as homemade, if you’re that hard up for one.
RV type vehicle. Maybe easier to code if the interior was a separate map. Maybe?
Separate maps (especially mobile ones) are nigh impossible with the map system Cata uses.
I used to code on muds. I've been looking at the source to see how different it is. Not that different actually.
Except they have a map system designed for multiple z-levels, (or are without a map at all if it's a text-based one,) which puts the problems in different categories.
Cata/DDA needs a massive map system overhaul for a lot of the suggestions that come about, and I have no idea if it’ll happen.