An invisible wall might not be a solution since the same space those survivors get knocked up to is another choke point. If the first ramp hit does not go so well, then a smoker, jockey, or charger can knock the survivors back down to the starting area at that location if that makes sense. The space right above the coaster entrance.Maybe a better solution would be seeing where the survivors are most commonly knocked to and maybe shorten those little wooden beams that stick out of the coaster? In my experience that's where I see survivors landing, those little wooden beams sticking out of the sides of the coaster that allows them to jump back up. I'm not sure I've seen anyone land perfectly on the actual coaster up top.
Why not remove the coaster in general? It has no loopy-de loops and therefore not worth the wait.
This has nothing to do with the scenario. As i think from this, its a luck factor. Leave it the way it is, and if it happens in a tournament it will be dealt with then. No need to change or add anything. I don't think anyone would care enough.
I think the entire map should take place on a coaster.
At first I had the same thoughts as KOrange: that it would be impossible to block this without also blocking pull downs from the rooftop. But I think I thought of a solution that might block most of the cases. If it works I will include it in Promod 4.4.