Its usually unfun because in many games, it requires some large expenditure (rec centers, indoctrination centers) to maintain colony happiness. Such centers do nothing else, and its just a base expenditure in "hammers" required for any colony. Basing happiness on military protection is kinda nice, because it fits well with local defense garrisons and what not.
If revolts are included in some way thats interesting, super duper!
I do like the idea of using espionage teams to purge heretics.
Or, as I would call them, Inquisitors.