I'd say that at this point it doesn't really matter... Just get the thing fleshed out a bit more. I think you may find that you are actually wanting to do things with the rulers / npc on every step, even at some point you'll have so much to do that you'll be staggering the processing, yes those things may be farmed out but it sounds like the brain is in the ruler and it will have to regularly make decisions based on what is happening realtime, at least checking.
My first thought was to suggest thinking about an animation timeline, however you probably want to use a FSM (Finite State Machine) for each ruler...