It would be handy to add more tracks in BB, Temper VST will do that but PG needs to fix BB so it sends info to the vsts to sync with the host to stop the cursor looping on the first bar. You can easily drag n drop tracks from BB into Temper then regenerate another track in that BB slot, this will give you as many audio/midi tracks as you like. You can load your tracks from another project an generate BB tracks to fit.

So PG PLEASE fix this bug.

Here's a video of the Bug:
BB_Sync_Bug.mp4

You might get quicker response if you go to the BIAB Support. I've found them very helpful.

Time sync VSTi's have never worked in BIAB. So hard to label this a bug. Or is this something else?

I guess I'm stating the obvious, but it you need more tracks, isn't it just easier to use RealBand?

It Bug's me.

People get stuck using just BIAB and are a bit frightened of Realband.

Say in Kontakt you have a strumming guitar and you have different tempos, BB/RB won't send that info to Kontakt. If you want to make up your own track in EZKeys/Drummer you can't.
That's just a few examples.
It should be a good fix in BB and RB for the long run, it's a Standard thing in other audio programs, I don't think you will get anyone at all complain when they fix it, it will just open up a lot more possibilities.

So I will just throw a few more coins in

VSTHost sends the tempo, there is a source code available for it.

VstHost on the left the vst follows the host
Realband on the right the VST don't follow the host