After my last 4E D&D game in which I'm a player (Blackthorne, an 8th level Human Hunter), most of the group hung around to just BS about things. During this post-game chat I realized that knowing the rules too well really cramps my role-playing in 4E. When I know that doing a given action is going to provoke an AOO; I may do the action anyway, if I feel my character would risk it...but the meta-gaming still comes into play. Or if I know I won't get any combat advantage because I can't get into flanking, as it's written in the rules, so I'll just take the convinent spot rather than getting close and arguing with the DM about the opponent not really aware of me there or the fact that I'm still attacking his flank, but I noticed some of the newer players "try" various actions simply "for fun", where I tend to be more mechanical.
Durring this chat I realized that the core 4E rules more often than not, spells things out rules so clearly that for combat you almost don't need a DM, you could nearly always "logic" out who a given creature would attack, and cover and combat advantage and all other situations are so detailed that the definitions seldom leave questions as to how the rules apply.
I know as a early 4E DM, I was very frustrated by this as I felt like the rules were constantly tying my hands, and the rules lawyer players were almost running the game (I did say "almost"). So, I opt'd out of DMing for a while, until I finally came to my senses and decided to say "I don't care how the Power is written, that just isn't going to fly here".
These detailed rules, and the specific overrides really seems the heart of 4E's problems, I mean in war games like Ravenloft or WH 40K, there is no GM so it's a short debate between how to rule a given situation even when they are playing a "Me vs Them" game. I realized if the 4E rules were more vague, I would try more role-playing type actions and have to trust the DM to be fair about the actual game effect.
So, as means to encourage role playing in combat, Open Gateways is designed to have a sufficently vague modifier for actions, with some guidelines for players and GMs to follow, but not spell out the details of every action with it's combat effect.
In addition to the vague guidelines, I really like the idea of a single AOO per round; rather than one per creature (it is possible to increase this by Feats like Combat Reflexes). This way leaving a threatened space does not always guarentee that the creature would take the attack, intelligent creatures may save the AOO for a specific creature, or combat savy creatures could provoke the AOO with the member of the group with the best defenses, allowing others to move at their whim...possibly avoiding the possible candidates that may possess Combat Reflexes.
Combining the single AOO per round with more actions that provoke an AOO, like standing up from prone, or drinking a potion, with more role-playing for minor combat adjustments would bring more feeling (and excitement) of the previous editions back to the game.
I hear responses to this like "A good DM will simply adapt the rules to the situation", but I feel like I've seen every new DM in 4E make the same mistake, and I've played many GameDay and Enounters at stores in my area and see DMs making these same mistakes as I did. Which is why I feel the need to call this out as an issue...I think exhaustive rules have their place in a board game, but not in an RPG.
So, in OG I'm encouraging GMs to make a call, players can argue it offline and groups can set up House-Rules to govern situations. I for one, enjoyed these debates when they occurred and I find that the more vague the rules are the less likely a Rules Lawyer will attempt an argument, as the golden rule is "The Game-Master is always correct"...That said, some GMs are just a-holes so players need to speak with their feet in those cases.