btw was it ever mentioned if there were any other civilizations in the dune universe? the empire pretty much controls the entire galaxy right? so any external threats of a original-ish varity could concievely be added on top of the above mentioned... or would that be better for a thrid game idea?
personally i'm a big fan of the power grab-> management -> invasion by an external force story progression in most kindom building fiction. even if it is cliche and done to death. imo it's just natural progression... unless assaination or folly comes round anyways.