Correct me if I’m missing some setting or use case, but I think the way instrument tracks handle instruments with multiple outputs (i.e. more than one stereo output) does not make sense.
Let’s take a drum VSTi as an example. Let’s say it has an output for each kick, snare and toms, in that order. (We ignore the rest here.) Obviously, I would want to name the instrument track Drums.
The instrument sub-tracks for the snare and toms audio, respectively, can be named Snare and Toms, which is just fine. However, the name of the sub-track for the kick audio is Drums, and this cannot be changed without also changing the name of the instrument track.
When adjusting volume, pan etc. of the instrument track (e.g. in top of the inspector), I would expect to make these adjustments for an implicit group track that combines the sub-tracks. However, the adjustments apply to just the kick track.
I think these shortcomings defeat the purpose of using a multiple-output instrument track at all, so I rather stick to using a rack instrument in this case.
Designing instrument tracks as described above would be an elegant solution, I think.