Has anyone thought about doing this before? It sounds like a general optimization.
Create one plugin that creates an entity with think set to .1 seconds, then other plugins would use the API to add their set_tasks with "b" flag to the entity's think. Check for tasks registered in it and if it's time to call one, execute a function in the plugin that registered the task.
What do you think? If it's not a bad idea and can be at least a bit useful, I could try to come with something. Not sure how to execute a function in other plugin though and callfunc_x looks really slow.