It took a bit of playing around, but the sixteen faders of the remote layer on the mixer will now control the first sixteen faders in the Cubase mixer. There's more that can be done there, including setting up the Cubase environment to enable bank switching (or, at least, it looks that way), but that can be dealt with later.
Now we'd had a problem at Windycon with the mixer, because we blew past the board's sixteen inputs and we lost the USB connection to Cubase. I've updated the USB drivers and -- so far! -- the USB patching hasn't fallen apart, which is good. But there's still the question of what to do when you blow past the 16 inputs.
Well, there was a question until I walked around to the back and looked at the eight channels of ADAT I/O. Any old eight-channel mic-pre with an ADAT optical output can be routed in there and those channels can be assigned to the first eight faders in the second bank, so that will get 24 channels of input without too much trouble. (I don't remember if Dave's MOTU units have ADAT optical out, but I have a mic-pre in a road case that does, so now I know how to handle that.)
The problem is that you can still only send out sixteen channels to Cubase. But in the particular configuration we were in, we could have assigned Barry's three guitars to Bus 1 and Sally's drum mics to Bus 2 which would get us down to sixteen channels total -- we'd just be mapping Bus 1 and Bus 2 to a couple of Cubase inputs instead of channels 15 and 16.
So -- with a bit of outboard gear that I've already got -- I can get 24 channels of input (20 mic/line in, 4 line in) that can be sub-mixed using the eight buses on the mixer to some combination of 16 channels out to Cubase.
That's encouraging. :)