You can do this now with Tasks. If you set a condition of the Task to test for a particular Property Value this is equivalent to the 'event'. The Task will only get evaluated when a value in its condition list changes. The 'trigger' would be any of the actions contained in the Task.
I admit that sometimes it would be nice to incorporate a simpler interface for simple actions. If you have some suggestions on a better or alternative user interface for configuring something like this, let me know.