These things that exist or are planned all use some event-like constructs:
the plugin system
connections (i.e. buttons and gates)
the callbacks from common to server
the proposed refactoring to have “method-like” function pointers for objects and/or object types.
All of those things could be set up to use a unified event/callback system, which would:
benefit plugins by making it more flexible
get rid of ugly stub hacks
reduce repeated effort on the “method-like” system for objects.