I haven't checked your schematic, but this definitively makes sense. It's been done before, for sure. I intend on using it in a future project actually, though I'll be trying to do high-side. I know of a guy on endless-sphere.com who has powered some MCU projects where a momentary on button gives power to the unit before it then powers a mosfet to sustain energy.I don't think you need to mess with the switch turning the mosfet on. Just have the switch give power to your microcontroller, and deal with the fet during the microcontroller setup.
They're just low voltage schottky diodes