Could tidy up the project window with fewer tracks, since you dont have to duplicate when using same midi and plugs.
I think best implementation I saw was MixCraft on this - each instrument, even if just stereo, gets two outputs for each instance and works as if you had one multi out instrument.
But ProTools and Reaper are good too, not needing separate track types for instruments, you just use an insert slot on any track.
Is solution maybe to allow loading of instruments in insert slots on audio tracks???