I'm currently using Tekkit 3.0.3 to design an elevator intended to traverse the height of a tower that reaches the maximum height limit of the map. I've settled on using Railcraft's Elevator Rails to do this, since Railcraft 3.3.0 added a condition that placing a rail opposite the Elevator Rail will cause minecarts that stop on that level to be pushed onto the rail.
So far, I've set up a system where each floor will have a wall of buttons next to the elevator. Each button is tied to a Toggle Latch so the setting can be turned on and off. The Toggle Latch is then rigged to a lamp above the light to show which floor is selected, and also to a wireless transmitter that is synched with a wireless receiver on the appropriate floor. Hitting the button for Floor 3, for example, will turn on the redstone signal up at Floor 3, meaning the carts will now travel to Floor 3 before exiting onto that floor's rail.
I've run into two noticeable issues... For one, if you turn on Floor 4, and Floor 2 without turning off 4, you'll be sent to Floor 4. Secondly, I've been testing all of these controls based on having floor controls only on the ground floor. If I were to add these controls to each floor, then turning on or off the 'Floor3' button on one floor would have no baring on whether or not another floor has selected Floor 3.
I'd appreciate any input on how I can wire this. This is about the third wiring scheme I've been through, and I'm not opposed to ripping everything out and starting over if I have to.