When the first arranger came out that had drums good enough for me to eliminate the external drum machine, I was one happy camper. It used to be an essential component. As I recall the Technics PSR2000 was the one that finally had acceptable drum sounds. Before that I used a procession of drum machines, including several Yamahas and a couple of Alesis. However, all I did was trigger the stop and start from the keyboard and use patterns I created in the drum machine. They were timed to work with bass patterns and guitar and/or piano strums from the keyboard. I basically created styles in which there were no drums. By doing it this way it was quite easy to keep the number of styles down to a manageable number because just a few bass patterns work with a wide variety of drum beats.
What the arranger offered was fills, breaks intros and endings. When the external drums because expendable,I never looked back. The less gear to carry around, the better.
I suppose it could still be done the same way: take existing styles, eliminate the drums and midi to the drum machine.
Too much work and bother for questionable benefit, IMHO.
DonM