Wishes, wishes...
Here is my amateur drawing of what would work for me.
16 channels about 9 dedicated for RT/RD (that can be also substituted for MIDI)
I think PG limited number of these, because by design (at time it was designed) average computers would not have pulled more, or they would suffer. I think expanding it to about 9 possible simultaneous RT/RD channels should not cause significant pain to render.
And a secondary, independent midi bus, which would not re-assign channels and all settings (volumes/ FX etc.) would happen within VST, only to have master volume be available as control from BIAB mixer.
Misha.