What's vital to a "Dungeon Keeper"-style game?

[sukael]

Hopefully some of you folks have played Dungeon Keeper (or DK 2), or, more recently, Evil Genius.

Let's say you were to run a game of this type - 6th-level PCs, each with Leadership (minions!). What would you consider most vital to a game of this sort? What books would you allow/disallow? How would you let the players plan out their dungeon/keep (would the Stronghold Builder's Guidebook be sufficient?)? How would you design the itinerant adventurers to try and invade every so often? Would you actually play out every encounter with said adventurers, or leave some in the background as automatically handled/not handled by minions?

What would you do?

 

[Celebrim]

Impartiality.

I think that you need to dispense with the notion of a DM entirely, play the NPC 'heroes' from a player rather than referee perspective and use face down note cards to track resources. Resolve gameplay conflicts through charitable negotiation, and resolve ties with coin tosses.