Well, there goes those ideas!
The good news is I got it working though.
Turns out, the 12v source is NOT switched, its the ground that's switched! Now this does make things easier I guess, since now I can use a regular on/off switch to wire this all up.
Anyway, I pulled power from my cigerette lighter, and then use the switch to turn on the ground that's always on, and connected the lights all up to the switched ground full time. Now whenever I turn on the switch, a constant complete circuit is made, and when the switch is off, a circuit is only completed when the doors open.
So just remember now when you're wiring up stuff to the under-dash lights that the GROUND is switched, not the 12v source
