I'm not sure if I understood you correctly but you could simply create one event function that calls the events of all your plug-ins, example:

void on_ent_remove_event(ENTITY *ent)
{
remove_ent_from_physics_system(ent);
remove_ent_from_pathfinding_system(ent);
...
}

...
on_ent_remove = on_ent_remove_event;