There could be a second set of rules for skipping station in addition to leave condition.
Disclaimer - I haven't read the entire last year of this thread.
Would it be sufficient to have a check box saying "if wait condition is already met, skip station"? IE if your wait condition is "wait until cargo empty" and the cargo is already empty, the station is skipped. I imagine this would simplify the implementation since you don't need a whole separate section for defining skip conditions.
Or, are there behaviors people need where the skip and wait conditions would need to be separate? E.G. if your wait condition is "wait 30 seconds" there would be no way to skip the station (without adding an OR to the wait condition). But I feel like personally I could do everything required without separating the conditions.
Wait a second... hold on... I imagine a grid inside engines which you can place combinators in, with input ports from the fuel and cargo inventories as well as external circuit connections through the current train stop, and an output that can be used to set the train's destination...