This suggestion is based on a previous test of mine. I made an invisible platform (make the texture pure black, set to dynamic,etc)
give it the moving platform script (I think its one of the elevator ones, perhaps lift2?)
make and connect a series of waypoints that navigate through your tunnel system. (place the start on your platform)
set the players start position on the platform.
build your level, baddies,etc.
And let 'er rip!
If there's anything you don't understand, I'm sure someone will elaborate. Happy game-making!
I know I keep changing my signature, so what?