Admittedly, it's not all that developed, but I've been keeping a list for some time of all of my favorite games (past or present) and the features that make them so great. I've got the list to help me find the connections, the variables I like, and so I can combine them in interesting ways. Combining elements of different genres can result in really cool concepts. For proof, check out the upcoming Endwar.
Anyway, so the most recent addition to my list is a feature from Medal of Honor: Airborne. I can't wait to get my hands on the full game, because I've played the demo at least a dozen times (I beat it on Expert difficulty using nothing but a pistol, last time through).
Of its many cool features, one struck me as being directly applicable to MMOs and RPGs: seamless movement and interaction between outdoors and indoors within the same environment.
Think about it. How often in MMOs is an adventure area, a combat area in particular, both indoors and outdoors? How often do indoor settings and outdoor settings directly interact?
To clarify what I mean, let me explain what it's like in Airborne. The demo level is urban warfare. You're ducking behind sandbags and the sides of buildings as you fight your way down a city street. But some jerk's shooting at you from a window of the building next to you. You shoot him, but then some other jerk takes his place and fires at you. Enough of this! So you run into the building to clear it out. Enemies have flipped over tables to use as cover. They hide behind beds, or around corners. But, man by man, you take 'em down until you're standing by a window. Pow! You get smacked in the helmet by a bullet from outside. Some enemies in the street below have noticed you at the window and are shooting up. And there's an enemy in a window of the building across from this one who's firing at you, too.
Seamless outdoor/indoor interaction. The guys outside interact with those inside, and vis versa.
Wouldn't this be a great experience to have in an MMO?