In present 2010 BIAB, drums fills can occur for a whole bar. It would be great to get drums fills for only the two last beats of a 4/4 bar. 1/2 bar drums fills are often present in pro pop and jazz songs.

That would be nice. There are others suggestions along a similar line, including the idea to separate the drum fills from the subsection markers.

Have you ever tried using a hold on the drums for the first two beats, and a hold on the other instruments for the last two beats, except the drums, followed by a part marker? It can simulate a two-beat fill.