Sorry for the confusion.
Forget about the pipe; forget about the space station. (The gravitational effects of a "rotating" space station can be simulated with sector thrusts, which we have already resolved.)
The real problem is: How do we get the player to walk on the walls and ceiling as if the walls and ceiling are floors?
Here are the ideas I have either found or thought of myself:
1. Use attachment flags for orienting and attaching player to walls. (This is what the WoW mod did.) The main disadvantage is that JK pushes the player to the floor or ceiling if on certain surfaces. Also, jumping would have to be altered so that player isn't always sent in the +z axis direction.
2. Use physics flag for flying. This requires reworking the walking sounds, reorienting the player when the player touches a surface, adding the crouch and jump effects, and changing the acceleration/deceleration effects of flying to match those of walking/running.
3. Rotate the level. I suspect this would be infeasible. It would likely require many 3dos or would be extremely cumbersome to do in multiplayer.
4. Give up and work on something else.
What are some other ideas?
I am currently working on Idea 2, because I have not found a way around the automatic pushing of player and the jumping might be easier to handle.