I had the main out as a dry/monitoring output, the first 8 sub outs as Pad type grouping (kick, snare, closed hat, open hat, perc 1, perc 2, ride, crash), then the next 8 outs for engines. This would mean I can devote an engine to be either an instrument kit, or a loop player, with the advantage that if there's a hit in the loop player that needs to be processed with the sounds in the kit (for example, there's a wicked top layer snare that you want to mix with your main snare to process/glue them together)
I'd set up 8 tracks in Logic, one for each engine. Then I set up aux tracks for the 16 outputs used, but set them as hidden tracks so they're out of the way until they're needed.
Then all 16 outputs were sent to a master drums channel for final processing.
It was really nippy not to have to set that up for every project, and having everything mapped out already *really* sped things up.
I'd FRed the ability to name the outputs in Geist, as that would make choosing a sub out that little bit quicker, but no sign of that one being added!
My last couple of projects though, I've actually started with an entirely clean slate. It was kinda nice going to this, using Battery for the main hits and Geist for playing and rearranging percussion loops.