Back when I played D&D, our group did the following, and liked the way it worked/realism.
Before each round of combat, all players jotted down a short note about their action for that round. It could be dependent on other people's actions who acted before you. (Like, "if the wizard starts to cast a spell, I move to block him"). We allotted only a minute or so for this. Then we played out the actions from highest initiative to lowest.
You had the ability to abort an action and just take a partial/standard action (as opposed to any full round actions) if something unexpected in the situation changed. Thus if the orc fled the room [before your action because he had higher initiative], you didn't have to waste your fireball spell, but you also couldn't take an arbitrary full action instead (we assumed you started your original action, but changed partway through, thus costing you a part of the time slice).
We liked the system overall - This kept players for maximizing/overcoordinating, it still allowed for players to be surprised by their comrades actions in the heat of the battle (which we felt was necessary and real), and still accommodated some flexibility in changing things at last minute. And you didn't have to fully write down your action - we trusted our players just to put a few words describing the action, and have the integrity to stick to even a bad planned action.
Haven't playtested Novus yet...