Battery cables and electrical problems in general can be real pains in the butt. It could very well be the ignition switch (a thought you mentioned). I mean, the starter could be at fault, I am just thinking along the lines of trying the cheapest easeiest fix first. There have been emails on here about how to jumper the starter relay, but I am more concerned about the electrical dead issue. That should not be the starter. Anyway, I still say my first two options would be the cables, then the ignition switch.

Check out this article: http://www.4x4wire.com/toyota/maintenance/ignition_switch/

Good luck,
Jim