There's now a working pipeline for creating custom props and getting them into the map. Currently, visible space optimization is underway. There's definitely some weirdness with the source engine when using func_areaportals - stuff that doesn't seem to be covered in tutorials. Trial-and-error is time-consuming, but is working so far. I'll see if I can get a working build slapped up somewhere in the next week or so.
Status of our Team Fortress map CTF-Borderlands (tentative title):
Layout: 100%
Flag Functionality: 100%
Door/Moving Props: 100%
Props/Static Details: 75%
Textures: 100%
Powerup Placement: 100%
Optimization: 25%