So back on the breaker / disconnect ideas, this looks nice, as it accepts 1/0 wire directly:
Lightning Audio LCB200 Larger than 100A total fuse rating Circuit Breakers Amplifier Installation Car Accessories and Installation Car Audio and Video - Sonic Electronix
200A sounds like it's probably plenty for the starter (yet still way way below short circuit current), but I really need to measure the current draw when starting my car to verify (with one of those clamp-on amp meters, I think I have an attachment for my multimeter for that around here somewhere). Looks like a decent solution though, and any time I'm working on something on the car that requires the battery be disconnected, I can just hit the manual trip button.