How are you going to enforce any of that? Boarding procedures you can enforce because the agents control the flow of passengers into the aircraft. Any disembarkation protocols would depend solely on passengers listening to instructions, feeling cooperative, and being willing to act against their own apparent self-interest (e.g. your every-third-row idea; who would stay put?). In other words, fat chance.

Just look at what happens when an FA makes the tight-connection plea on arrival -- somebody in the back of the plane has to make a honeymoon flight, please remain in your seats and let them off first, etc. At least half the pax ignore it, and there's nothing you can do about it.