The Ogre and the Fighters should have to roll some dice to see if the Ogre can push past, and the attempt to push past should be a full-round action - nothing to do with attacks, more like blocking in US football. The Ogre might have to choose between spending the whole round just trying to push past or clobbering one of the Fighters instead.I like attacks of opportunity because I really hate the idea that say, an ogre for example, could win initiative, and wander past three ranks of fighters and squish the mage. Especially when I'm playing the mage.
Attacks of Opportunity are important in making melee fighters actually useful; of the fighters can't protect the casters, what good are they?
And this points out one of the main hazards of turn-based play: everybody freezes except the one whose turn it is. Easy for play, but not the least bit realistic.