First look at G54 - G59, work offsets
Pneumatics is a really bad idea for positioning. Air is compressible and not good for positioning. Hydraulics would work fine, but certainly would not be my first choice.
Some type of electro/mechanical drive system would be the best, a lot of options available, depends on the rest of the system design. Read the position with an encoder attached at the appropriate spot.
Overall, what you want to accomplish seems very doable and not terribly difficult.