FWIW here is my idea of the perfect BiaB VSTi.

For the MIDI side I view the VSTi as an input device much like a MIDI controller. That is using it to drive data into your DAW. Thus you assign a VSTi in your DAW and each BiaB VSTi MIDI track would power each different DAW track. Again that is much like making zones on your keyboard controller. After you achieve the perfect BiaB VSTi track you would or could move it to your DAW. What you hear in the BiaB VSTi is exactly how it will sound in your DAW.

My reasoning for this is that GM is not used much outside of the PGMusic world. MIDI users usually would have much better sounding samples than what comes with GM so having to listen to a VSTi that only uses GM might be a major step backwards for them.

For the RT side the above isn't necessary. Just generate your RTs then move them to your DAW.

For styles with both RTs and MIDI a combination of the above ideas would come into play.

This is just my view and others may or may not agree.

When you are at the checkout line and they ask if you found everything say "Why, are you hiding stuff?"

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware