Would be cool. I had some ideas about this, but never really got around to posting them. Basically, the elevator I thought up would make routine visits to each floor, going up and then back down. You could place a trigger on a brick in front of the elevator, and when you step there the elevator "knows" you want a pick up. It will immediately head for you (after it waits the normal time at its last stop). If someone else moves over a trigger, that's before your level, the elevator would stop at the other level first.
Upon entering, no matter how many people there are, they will each be asked a number (depending on the amount of levels). It then continues on its normal path, if it was going up, then it would continue to go up. However, this time it would skip any floor not present in the list of numbers it was given earlier, unless, of course, someone called on a floor that was along the way. People would also need some notification that they reached their destination because of the fact that the elevator can stop anytime to pick up more. Another check would be for the number of people on the elevator. Again, the elevator "knows" that no one else can fit on, so if a call is made, and the elevator is full, then it will pass you.
How could it be set up? Well basically, you have a new type of spawn for them. Like a vehicle spawn, only its a border around a hole. Like this:
The border part would look like a normal brick surface, and the center would resemble the width of the shaft. When you hit the brick with a wrench, it will spawn an elevator, maybe of your choice if you want variation, and then tell you to apply things such as group name, level number, wait time at this stop, etc. Like the portal system, this elevator will only respond to things in there group. To make it so people can't mess around with someone else's system, you would make it check for a name that's being in use, and someone who is trying to use it, and then do an ID check to see if they match. If not, don't let the other person use it. So you don't get any complications, with your system, a check would be made to make sure all elevator spawn bricks are vertical of each other. The trigger brick would do a radius check, every time it was activated, to make sure the floor it's effecting is close by. If not, it wouldn't perform the call.
People entering the elevator shaft when they are not supposed to is a big problem. Basically just copy the decollision style of the door creator. Make it so when you wrench/use a tool of some sort, on the bricks you want to be doors, it asks for floor number, group name, etc. It will open when the elevator officially stops, and will close right away at the time it leaves.
There are probably things I forgot, so you might notice complications that I missed and didn't add anything in for.
I know it's a lot to read, but if consider doing this, it might be a good idea to read if you really want to make an effective system.
