Wall settings at anything but 90 degrees would need a modelled wall, but that could be as simple as an entity that is simply a corridor. Diagonal walls at 45 degrees could be done using segments.
There are already ramps IIRC, I know for certain that there's sloped roof sections - and climbing on the roof should be possible. The collision system is pretty good, the guy kinda clambers over everything so slopes should be easy enough to work with.
The levels are 40x40, so that's the minimum and maximum size, it's upto you how you lay the level out, prefab rooms are created just like levels, you'd actually design the room in the top corner and export it as a prefab which could then be dropped anywhere on the map.
Van-B

It's c**p being the only coder in the village.