I suppose you could build a custom relay box and use power-on time to get the mirror to dip when the car is put in reverse, but the real (and difficult) solution is to rewire the doors for memory, acquire memory mirrors, memory control module, memory harness and seats. Going the route of the custom relay box: without having the potentiometers in the mirror, you'd also have to leave the pass mirror in one position all the time, so that the timing didn't get screwed up on the dip and return to normal position.
I also have to say, it's a marginally useful feature and is mostly an annoyance. Like park distance control.....invented for drivers who don't know how to park the car.