John-Luke:

You said: "I'm not sure to fully understand your proposal. Could you detail or provide an example."

When PGMusic records a musician for a RealTrack, they must typically record CHORDS or at least multiple notes at one time. So for example to record a guitar RealTrack, they would need to record him/her playing a C chord, C7 chord, Cmin chord and so on for a goodly number of different chords. And then do the process all over again for every key (unless they use their "transposition magic" for other keys - I don't know).

In any case, for them to include slash chords, they would have to record considerably more, to get (as you suggested) C/E, C/G etc. chords.

All of that pertains to guitar, and any other instruments where you typically play more that one note at a time, like piano.

However for playing the BASS, like electric bass, double bass etc., you typically only play ONE NOTE at a time. So when BIAB shows C/E in the chord sheet, why couldn't it be programmed to just play an E note there? It's just the bass instrument that needs to ALWAYS play what comes after the slash.

I play the electric bass.
When I'm following along on a chord sheet (or BIAB chord grid), and I come to a C/E chord, I typically play an E note, as that's what the composer expects to hear from the bass.

Perhaps I've misunderstood what you're trying to get BIAB to do.
Good luck!
LLOYD S