Perhaps a more \"turn-based\" battle mode could be implemented. Not as static as a Final Fantasy battle mode, but something more like Quest 64.
In that game, when you encounter a monster, the map you are playing becomes surrounded with an octagonal field of movement. In that, you and all the enemies have their own \"Action Octagon\" as well. Within the octagon, you can move, use spells, attack, etc. If you wish to go further, you walk to one of the octagon\'s sides and use an action or simply end your phase. That way, when your turn is up, your pctagon would have moved, to center over your character.
Now, to make this system actually reliable on a MMORPG, you will need a more open mode of this.
Lets say character A finds a huge low land basilisk. The game asks the player if he wishes to enter battle. If the player says no, he can go away. However, if the player is too close to the beast, the battle starts anyway.
Then the two start fighting.
But then character B shows up from a nearby cave, and wishes to help the unlucky character A in his battle (and hoping to get some reward as well). Then B goes to when the battle is going on, and the game asks him if he wishes to participate in the battle. Here different things could happen.If he says yes, he goes in, and follows the same rules as A. If he says no, and is far away enough, then he can go away. If he is too close, and the basilisk is currently distracted fighting with A, he can still escape, unless the basilisk turns and finds him. Or, if he says no, but is too close and the basilisk is currently centered on no one, then B is dragged into battle.
This is just a vague idea, if something like active turn based is ever used.