Hold two microcontrollers in reset at turn-off with one DPDT power switch?
Forgive me if you've already tried this, but from what you've described, it sounds like you should be able to pull it off with just a switch and p-type mosfet like this.
That way, uC1 can trigger a reset with its GPIO, and not reset itself. Definitely throw pull-ups in there too, I've left them out for the sake of showing the principle.



simulate this circuit &ndash; Schematic created using CircuitLab