Elytra droppers would be 12/10 but yeah, not possible. Anyway droppers are a small challenge that could be added to the parkour server and I wouldn't mind seeing this implemented and I think a lot of players would love to try them out. Though it would be a HUGE benefit if players would submit their own dropper maps instead of the build team creating dropper maps, as in my view, there are more important things to be created for the server. Maybe I'll make my own in my spare time.