Assuming the rampant problem of modified client use continues into the 2018 LTS/Udon release, Udon powered worlds will become a new target for illegitimate RPCs.
World creators should have a way to declare which custom events are activatable remotely with a checkbox on the custom event Udon node. This should stop malicious users from ruining minigame worlds, for example.
This could be further secured with 'master only' or 'owner only' options like VRC_Trigger and a dropdown option on each custom event Udon node. These options also need to be available in Udon assembly for external tools like U#.