Thanks guys, yes, working in midi seems to be the most predictable option. Unless some of the realtracks can handle more chord types perhaps.

I might experiment with exporting wavs to DAW and then tweaking the odd notes here and there.

It's puzzling that BIAB doesn't support setting scales for certain bars, as musicians think in scales all the time.

Maybe by creating a muted melody track to define a scale for some bars could work?