Either the switches activate the battery or they activate the trigger circuits (probably both).
I should also note that, unless you had extremely detailed pictures of the switches themselves (or part numbers), you could easily use a combination of switches which appears to do one thing but instead does another, so X-Rays and a wiring diagram wouldn't necessarily be helpful in discovering the actual path of electricity. You could maybe do something clever with a very sensitive electrometer, but that would take way too long.
Arming it doesn't seem like the hard part to me. I think the hard part, with all the foil based triggers and spring loaded screws, would be construction and QA and making sure you don't kill yourself activating the thing because there's some filings completing a circuit you didn't know about.
I should also note that, unless you had extremely detailed pictures of the switches themselves (or part numbers), you could easily use a combination of switches which appears to do one thing but instead does another, so X-Rays and a wiring diagram wouldn't necessarily be helpful in discovering the actual path of electricity. You could maybe do something clever with a very sensitive electrometer, but that would take way too long.
Arming it doesn't seem like the hard part to me. I think the hard part, with all the foil based triggers and spring loaded screws, would be construction and QA and making sure you don't kill yourself activating the thing because there's some filings completing a circuit you didn't know about.