I will admit upfront that I know very little on this subject. However, would it not be possible to put RealBand into the process?

Could you not put the first set of chords (say with the Cmaj7 et al) into BIAB then export all the tracks to RB?

Next, do the same song with the alternate chords (say with the Dmaj7 et al) in BIAB and export only those tracks that would be affected by these new chords? You could omit the drums and perhaps the bass.

Would they not all play the way you wanted them to in RB?

Good luck!
LLOYD S