Originally Posted By: VideoTrack
I imagine that this might be technically difficult

Realy ?
It's a basic function in all DAWs I know: the IMPORTANCE of not stopping the PLAYBACK during the maximum of possible changes: phrase, plugin, preset, tempo, pitch, editing piano roll/mixer/arrangement ...)
But it's true that BiaB does not work like DAW, moreover it's one of its strengths.
& in BiaB, we can change the instrument "Select MIDI instrument (patch)", which seems to me (changing the instrument) technically more difficult than changing the track (the MIDI phrase)