ServiceChanges is overly complex. In my perspective if GTFS-RT matches the
SIRI-PT/ET structure it is trivial to do a detour (if the journey planner
would allow it). Sure people can argue: Then we cannot have "pretty
shapes". Shapes aren't pretty, and map matching becomes a requirement
anyway. Then we cannot have new stops. Ticketing systems cannot introduces
new stops on the fly either, so having a stable network in GTFS is the
basis of doing detours right. If the situation is so bad that everything
falls apart and the data is available to fix it: just introduce a new
timetable.
I don't see why removing functionality would have priority over first
implementing the alternative.
--
Stefan