Henry,
First of all welcome to the forum! Heard a couple of your tracks and the one that you posted in User Showcase recently. Good stuff!

A few days ago I watched the video you mentioned above. We have very similar setup and methods. Yes.., it is valid workaround, however...
To solve specfically this and several other acrobatics 2 components are needed.

1) more available mixer tracks in BIAB (16 sounds like a perfect number:))
2) bar freeze (aka bar to bar regeneration)

There had been several heated discussions about adding mixer tracks, the latest is here:

https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=600974&page=2

Dr.Gannon replied to that topic by saying it is technically possible. Not sure if it will be implemented soon or not(or at all)... It is my biggest wish for BIAB... If you think it will be usefull to you, and I have a feeling it can be, kindly support this idea in the forum link above.

Misha.