This is already possible. I have been bouncing to New Track with this new external Instrument feature.
It is in real time, so it will play through the whole track for every track you are bouncing. Once the bounce is finished, it mutes the clips on the instrument track.
The only thing you need to watch out for is to either bounce any multiple clips in the track to one large clip, or extend the end of each clip because every time it gets to the end of each clip in a bounce, it stops recording that clip straight away and you'll miss out on any decaying sounds the instrument is making after the end of the clip.
This is an example of the bounce track below (I'm having an issue because even if the instrument input is set up as mono, it is capturing in Stereo, so I'm making a request too :)