[ReThink]

Also, a trap could be where the ts can make the elevator fail and fall to the bottom of the shaft and kill anyone that was in it.

Eh, that's not a good gameplay idea. Making the only way up a trap will discourage players from going down->up and up->down, effectively separating the map into 2 pieces and isolating players, overall leading to a not-so-wholesome experience.

An alternative is making the elevator stall/jam for a few seconds, allowing T's to kill anyone on board/toss grenades/ prevent people from chasing them. This both allows transport, is fair to both sides, and adds an interesting gameplay element,