Based on quick guesses..
This seems to have the main "meat" of the map format.
It's somewhat BUILD inspired, being sector based and relies on 3D polygons.
Sector looks for faces, faces look for polys and so on..
Kinda reminds of build looking for: sector -> wall, wall references the next wall, etc..
Editor would need to be similar to a modelling program and it seems that you'd need to be able to define sectors individually too.
Basically something you might want to create from scratch, but would take quite a bit of time.
Devs likely had the level data in a different format with their own editor, before it was "compiled" to what it is.
Manual labor. Hope to see it some day but I just want to be clear here again that Console and DOS version share nothing in their engine.
Source code / tools for any of them won't help the other one.