I've not tried it personally, but the codes for much of the arranger's basic operation are in the MIDI parameter chart. I suppose, with a combination of FC-7 AND a MIDI foot controller, you could get more than the seven options the FC-7 allow.

One thing I wish Roland WOULD change though, is that the FC-7 assignments are global, per UPS (whole memory load), whereas the normal footswitch assignments are per UPG (registration). This is something that Roland could easily rectify on the next model, and stretch more use out of the basic seven switch FC-7.