I just checked mine and, unfortunately, it looks like the groove functions are the only parameters that can't be controlled by the ribbon. But definitely, the ribbon does provide a nice workaround for all of the other ones.
I was just gonna say, you'll definitely want the SCSI board. I found it to be a rather crippled machine without it, one of the coolest ever with it. Pssst.... I just happen to have an extra one I'd let go super cheap if it turns out that you need one.
Here's a link that talks about replacing/cleaning encoders for the A3000. Having both of them, would you say they look like the same encoders on the SU-700? Heck, maybe if you really needed to replace a couple of them, you could pull a switcheroo with your A3000. And if nothing else, hit them with some Deoxit.http://todbot.com/a3k/knobs/
Finally pared down to 3 machines and no GAS for months!
Tempest | Spectralis | MV-8800
I have a 64 patch Tempest soundset for 10 bucks, Here
(16 bass drums, 48 synth patches)