What I want to do is use BB to generate tracks, then replace those tracks with me playing. I have not figured this out yet. (I'd say I'm disappointed but I know it's my ignorance, not the program's capability, which is pretty impressive.)
That is exactly what I do. I usually only keep the BiaB drum track and replace everything else with either myself and/or others playing. You may want to check out my songs in the user showcase forum.
But that is impossible to do with BiaB, you need a DAW. If you do not have a DAW not to worry as BiaB comes with Realband and that is a very good DAW. I do not use Realband however there are many Realband experts here that will gladly help you if you need it.
Remember the only stupid question is one not asked.