Well depends if the Occupiers have a different state religion from the people they are occupying you can basically use that for your advantage The European wars of religion between Catholics and protestants are the best example you can pick.
I've always wanted to run a historical mystery/detective role play. Something akin to Name of the Rose, a locked room mystery set in a single local, where the players have to figure out who killed a particular NPC. Or alternatively something where everyone plays as a medieval peasant trying to find out who's responsible for acts of witchcraft taking place in their village.