Why not use stainless bolts for the lugs? Corrosion wouldn't be a problem, and I doubt the conductivity difference would be an issue (all stainless bolts in the ForkenSwift's circuits). But maybe I'm missing something. You can get brass bolts if you want - Paul got some for his controller project.
Those blade disconnects may not be rated high enough. If you have a collision that dead shorts a cable, the current will be higher than 500A. But you'll also have a fuse in the pack right?
As well, I've read about some conversions using an inertia switch. Like this:
Switch, First Alert Inertia, recycled . But it still requires a main contactor or knife switch setup like you're imagining.