I made a map like this about a month ago
here. There was a problem with people getting stuck in the cart very easily as it moved up/down, and it could also push players into buildables/props along the cart track at any given point. There is also an issue with overtime + koth + payload, that I never was able to fix, where it spams OVERTIME 3 times a second until overtime ends. (Funny for the first 10 seconds, but not at all beyond that).
So you should keep those things in mind: try to keep vertical turns as smooth as possible, try to keep things away from the track, and possibly design overtime out of the map or try to find a solution to the sound bugs.
Goodluck.