If you are going to use BiaB you will need to become a big fan of "BB & The Workarounds" as I'm usually the one the has to come up with workarounds frown BiaB is awesome how it can stitch sections together musically, it just falls short in the workflow compared to what can be done with those sections in a DAW.
The way to solve the issue is:
1. Put a lot, lot more work into Biab (years frown )
2. Get the BBPlugin working fast with Alt+F8 and without creating gigs of wav files. (could of been done by now)
3. Give the BiaB track data txt that will load all the tracks instantly into Reaper. (could of been done by now)

The only stereo files that display as mono are the overheads and room tracks in the Mutitrack drums.