Missed the first mistake I noticed watching the film.
Neo and Trinity standing on top of the elevator filled with explosives.
The grab the pulley cable, and cut the other, sending the elevator to the ground.
The problem? One of two things could happen:
A. Elevator hits the ground floor before the reach the top of the shaft, meaning they would no longer be being pulled up, and would fall down the shaft themselves.
B. They get to the top of the shaft before it hits the ground, splattering them into the ceiling and/or pulley/axel.
Solution?
An "Ooh! Aah!" slow-mo explosion to distract the audience.
Im sure that would be quite easy to avoid. If they wait until just past half way up the building(you should be able to see how many floors the elevator has) they should reach the top.
The second problem you mentioned is easily avoidable by letting go of the pulley at the right time(they will still be travelling up when they let go and will take a few seconds to slow down). If they know theyre going too fast the just let go earlier, im sure neo and trinny wouldnt mess up the timing considering who they are.
The more i think about it....... they probably would have cut the cable before the elevator reached half way.............who cares
