<< One of my most annoying issues with BIAB is regeneration time.
With any small change I sit and wait and wwwaaaaiiiittt... Life is precious, but I do not feel that when I am just looking at the screen waiting for regeneration to finish. Trying out things, I could make well over 100 changes in one tune that I would want to audition.
Ideally I would want regeneration times to be a fraction what they are now... About 75% faster.
My computer is fast enough

>>
Here's some suggestions that addresses these issues you have while remaining completely within BIAB - No DAW's allowed. (In Creating tracks not editing)
. Starting with your initial Chord chart and Style selection - Save it in a dedicated project folder
. With every change you make that you are somewhat or completely satisfied with, do a Save As and save that version of the project to the dedicated project folder
. You are saving the above projects saved at different completion levels so you can always revert to a prior project level if things get messed up with auditions and instrument changes. You do this because you can program in dozens of changes and instruments in a single generation of a BIAB project.
. regarding Regenerations - Rather than waste time by generating each and every single change, use the Chord Chart (particularly the UNUSED BARS Section) to enter your chord change experiments and instrument auditions. You can literally generate 100 chord changes in a single generation and at the same time do it with dozens of instruments. Regeneration times would be a fraction of what they are now. . .
For example, if your song is 90 bars in length, There are 165 unused bars that can be utilized to program experimental chord changes, chord progression changes, marker changes, tempo changes, shots, holds, rests, etc. These would be placed in the unused bars below your song chart and could be deactivated before rendering your song but also rendered if desired to be inserted and used in your project.
You can reconstruct single bars, multiple bars or entire sections. Generation time will increase a few seconds but you will have generated possibly dozens of snippets to audition and save for use in your final project. Every time you regenerate, these extra bars will also generate so multiple regenerations will result in hundreds of possible snippets.
Simply by using a feature in the Mixer Tracks that allows up to 10 instrument changes per track, utilize this feature to have specific instruments to come in and out at various bars which will force the BIAB search engine to more creatively and randomly search and select that instruments audio snippets.
. For example - Alternately place a banjo and guitar on a track so that they change every two bars, every 4 bars, every 6 bars and every 8 bars to create different phrases within just 8 instrument changes.
Hopefully, there's something in these suggestions that will aid in speeding up generations in yours and others workflow.