Well I think we all agree that Pipeline is a proof of concept at best and really a shame for valve. I think it can be saved though.
IMHO the biggest problems are
- Forced Spawncamping
- Next to no chance for a comeback
My suggestion for the second issue is the following: Throw away the two carts concept, but make it one cart rolling in either direction. No rolling back, whatever team is near it pushes it, both teams is a block of course. There might be a need to reduce the speed but playtesting will show that.
The cart starts in the middle now of course.
Thinking about it, maybe rolling back towards the middle ain't that bad, gotta try that too.
Spawncamping will be harder to fix, however a quick fix for stage two could be to move the end point to where you get up on the first floor, "hidden" stairs, after the tunnel exit.