I once ran a small-ish forum. It sucked. But now? I'd definitely run it differently. Like back then I just had four or so people @ admin and it was basically like all of us did whatever and spammed anyway publically and it was basically just like "we're not PC but we sure like to discuss PC a lot" lol :x
Either way, what I WOULD do, is ensure that people are doing the work they're meant to, and the deserving people get the deserving positions. For example, even if there were like 6 people at the rank above moderator, I'd still let someone else go there if they were truly deserving, or if I felt someone else didn't deserve their position (if they're higher - because I assume I'd only really demote the ones that are really inactive). I'd just move them down and let them mod the forum of the choice. They can't ask for modship at first, but once they are a mod, then they can ask for another forum if they feel they deserve it, are active enough and help out enough there. Everyone at every rank would do what they're meant to do, basically - I'd probably be the main one in control to enforce this. There would be basically like three ranks, where it's like admins, aka co-admins, so maybe two others, then there would be something above moderators, similar to smods here, but powers would be a little different, as in everyone at any rank can make decisions for the forum and bring them up, and everyone at every rank can bring up who should be modded etc, and it would be voted on democratically. However, I'd get the final say if someone wasn't pulling their weight and didn't deserve their position. Yeah, I'd run it this way no matter the size, really.
As for rules... the things PC has I guess, though a lot would be down to what the moderator thinks, for example, there would be no four word rule, but rather a "do not spam" judged on what the moderator says. Oh, and fair. Not to disrespect people would be important, and I'd imagine everything else would be similar to PC, really. I'd just want everything on this forum to be as fair as it could really I guess.