Have a "drum fill" icon in a tool bar that opens a window to set parameters on how you want the fill;
For example:
A) In one bar, give the choice of full bar fill, 1/2 bar fill, 1/4 bar fill.
B) Toms only (Or any other drum part) and/or combination of drum parts (Hi/Mid/Low/snare/Kick/cymbals)

The advantage would be for example: you have 4 bars of the drums using only the Kick snare/Low tom with a splash of some cymbals)

There should also be a drum fills manager window, to setup regulate the round robin repeats (On a per song bases). So if you have 6 fills, you select only the ones you want to use and also could set the one you specifically want on a specific bar.

Robert cool