So, It was always annoying on some instances, that lifthills will power trains up again if they roll back.
For example, this is a recreation of a common japanese Shuttle-Coaster wich will not work in RCT2 as of yet because of this perticular Problem.
The train will be stuck forever moving back and forwards o top of the lift.
This would ESPECIALLY be helpfull on coasters like Kingda-Ka, so trains wouldn't be stuck after not making it over the top but rather move back into the station / brakerun again. Or launch coasters with multiple launches till they make it over the top (like Skyscream @ Holiday Park, Germany)
Another suggestion:
A forwards starting Shuttle Mode. Wich will drop trains once they reach the lifthill top moving FORWARDS out of the station, rather than backwards.