Ok I'm with ya, I just tried it and yes it's useless rendering the midi to wav, but that should all change now and won't do that.
And yes in Biab VSTi you need to be able to send the selected track generated midi to a virtual instrument while it plays back in sync. All the midi tracks would be on a different channel but maybe right clicking the midi track in the Biab VSTi you could rechannel it ?
Same as in the Biab VSTfx you need to be able to send the selected track generated audio like "Direct Input" MultiRiffs to say Amplitube/Guitar Rig while it plays back in sync with the other tracks in the DAW, this way you get to see what riff fits best playing back with the effects added live.