Jim,
There are thousands of user and third party created styles. There are plenty of converters that would just extract these to Midi sections parts. Unfortunately BIAB styles do not have much focused content for intros, fills, or endings. You have to craft it yourself with A/B, breaks holds etc.

I do have big expectations for Utility tracks, and hoping they will gain properties to make it possible to create these (intros, bridges, etc.) with ease from existing pool (*that means without workarounds!)

What pipeline suggested, could make it much more interesting. As you could have a Midi User track, for example for intro, that is specifically made for intros, that you would simply put on a single mixer track and mute at the bar where needed... and it would follow your BIAB chord sheet.