Thanks for posting the pictures. I love the look of those pro devices and what you've done with the Raspberry Pi looks really interesting. Can you use that to control what it plays as well as showing that it is playing? I know @kgallen has a number of the pro Sony decks (the rack mount ones). They also have RS232 serial ports on the back. I wonder if they could connect up in the same way?
Anyway, should probably save the questions for your new thread.
In battery related news, my gumstick kept going until 10.30pm last night, when I finally turned it off. I got another 2 hours or so out of it this morning before it finally gave up the ghost for good. I think in total I got about 14-15 hours out of it, although for around half of that it was displaying the low battery indicator. When I tested the voltage at the end it was 1.228V but I couldn't coax it into playing any more.