Using the Band in a Box daw plugin in Synfire?

I've used the BB DAW plugin within Cubase, and found it to be not quite as advertised...buggy, quirky, unreliable, etc.

This was at least a few years ago, so maybe PG Music (creator of BB) has gotten their act together by now. Stranger things have happened.

BB is not really an idea generator per se. In the audio realm, it plays back various pre-recorded phrases in the manner it best "thinks" will work in the current project. (Sometimes this can work really well, and at other times not so well.) That's where I have the most experience with BB, but my guess is that BB's MIDI functions work in a similar manner. You pick a style you like, and BB will adapt that style's MIDI parts to fit your song. My guess is that MIDI parts will generally be more adaptable ("plastic") than audio parts. But it's not really generating an idea from scratch. 

This doesn't mean BB can't be useful paired up with Synfire. But it seems to me you'd have to export the BB MIDI parts and then import them into Synfire, which can be cumbersome and a flow killer. I recall that a while back I wanted to figure out some way to use Stochas simultaneously with Synfire, but again, one would have to export the MIDI from Stochas and then import it into Synfire. That's just the nature of the beast. 

1. I don't think BB can send MIDI data directly into Synfire. That's not the way Synfire works. Synfire isn't a DAW, and all MIDI notes must first be converted into figures (or static pitches, which again are not MIDI) as a first step. I'm not an expert and I could be wrong, but that's my understanding.
2. I think the way FL Studio or any DAW plugin works in Synfire is that the plugin can have as many audio tracks as that plugin allows, but they will all be fed into Synfire, which can then output them only via a single stereo track. This can actually work quite well. You do your mix within FL Studio or whatever, and then add and mix various Synfire parts for the final production.

I'm aware that there's a language difference here which leads to some confusion, so maybe that's causing me to misunderstand what you're trying to convey, or you to misunderstand the meaning of various things.