There's an FC-7 input on the BK-7m. Seven switches you can assign to whatever you need for foot triggering. Plus the unit seems small enough to mount right over the keyboard you are using to trigger it, and the layout seems to put all the main buttons you need on fairly big buttons, right at the front of it. Take a look at the layout, again, Scott. Things seem a LOT better than those old RA units (I had an RA90 for years) ever were.

I am not sure that this is really the right thing for someone that wants to use a controller and JUST this, as you say, might as well go for a regular arranger, but for someone wanting to add an arranger capability to a nice WS, or MIDI guitar, or MIDI accordion, etc., it's a well tested form factor.