as far as I understand, the original BIA sounds a tiny little different, but not really recognizable.
I heard it shall sound 95 - 99 % like the original one, just differs because a other chip was used.
I guess the most people dont identify the difference in sound.

I still have the old one.

The new BIA is a copy of the old one with additional features and swappable firmware to load the other vco-modules on it.
New one is better because of the swappable firmware.

Can I build a bass/drum voice around it ?

Yes absolutely, but it is one on its own.
Many people build a rack just around it, it´s very common.