I have to warn you though, TF2 was not made with elevators in mind. The characters jump around while on a moving platform and if you are making a ctf map, the bag will float in the air. Some elevators won't even allow you to re-pick up the bag, making you wait until it re spawns. So if you can avoid this, go that way.
Despite that warning, it's not all that bad if the elevator moves fast. I suggest you use a func door with a lip for the elevator so it moves up (to make it go sideways, change the move direction), but disable use on touch. Then use a trigger with a logic timer so the elevator goes up after a few seconds. This will allow more people to use it at the same time.
If you don't want to tackle triggers, just leave it on touch. This will make it so the elevator moves on contact.