I'm on board, too. One of the most important things for me is that M&B ruined melee combat in every other game. I think sometimes about how nice it might be to actually be one of those soldiers getting bossed around; there you are, part of a shield wall or spear wall or whatever, with a bunch of chumps you don't know to the left and right of you, and together you have to win a battle that will matter tomorrow.
A couple more things I would like to see:
1. A huge, open world, where you could shun the trappings of mankind and just have a grand old time on a walkabout, checking out the sights.
2. Real weather and seasons (sooo important to me). Think about basically every RPG you've ever played; there was a wintery spot either in the north or in the mountains, right? Even Alaska and Sweden have Summer. Fall comes, leaves fall, it gets cold, and then snow comes. If you're not properly dressed when you go outside, you should suffer performance penalties. I tried Age of Conan, but I couldn't stand all the miniskirts in the snow. I'm from the north, by the way. Imagine also what it would be like trudging through the mud on a cold, rainy day, and suffering movement penalties.
3. Things that go bump in the night. Real things. Like raccoons. Or maybe bears. Who knows? Another total crap thing in MMOs over and over is how you have to go kill that lion with your sword. Give me a break. Make animals fast, make them clever, and put them in an ecosystem. Lions eat zebras, right? Don't turn them into mobs that inhabit different places. Create a balanced ratio of predators to prey, and let them wander around. If they get close to each other, let them behave appropriately. If you're in the wild, checking stuff out, and you see a bear, you SHOULD be concerned. Let's make large animals dangerous again.
Anyway, it's brainstorming like this that helps us realize how formulaic MMOs are, and just how much they can/need to develop. First thing we should probably consider is dropping the term MMOS and sticking with persistent world; that can go so far as to include ArmA, for example, and that removes the glass ceiling that's been stumping all the naysayers about this concept. Why couldn't you have a persistent character in a medieval version of ArmA, for example, and just take it in a different direction than they did? Sure, it raises a ton of questions, but you sculpt your idea by the answers you choose. This, I think, is exactly the kind of thing PC gaming needs to rejuvenate it.