You can play around with Aux Bus Set for RealBand and ReaStream https://www.reaper.fm/reaplugs/
Reastream will send midi/audio to other tracks, other DAWs or other countries.
You can send tracks to a master track and use node volume control.
Combine them with MiniHost and you can do all sorts of things.
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=538454#Post538454
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=501348