You're probably right Videotrack.
However, I can imagine a scenario in which multi-track drums could be used fruitfully without a major change in BIAB's architecture (provided that the drums performance were recorded with multiple mics, which I have no idea of course).
For example, I could compose a song in BIAB and arrange it with 4 or 5 drum tracks (1 per microphone) and then 1 bass, 1 piano and 1 guitar (just to have a general idea of the arrangement). Then I could save the individual drum tracks as wav files to be imported in my DAW. Then I could go back to BIAB, save the same song with a different name, and go back to just a normal 1 stereo drum track, and use the other 7 tracks for other instruments, as we do now (and, again, export as wav files the tracks I need for my DAW project).
In other words, for users that use BIAB in order to export the wav files to be used in a DAW (and these are the kind of pro or semi-pro users who would benefit from multi-mic drums tracks) it doesn't really matter wether you have 8 or 16 tracks in BIAB, cause they're gonna export those tracks anyway to theri DAW. You can always use different versions of the same BIAB song with different instruments.
The real issue is wether the drum tracks were actually recorded with multiple mics. If not ... never mind smile

Anyway, I think that having 24 bit is more important than the multiple mic drum track option.