To be frank, I was somewhat disappointed when Blizzard said that flying mounts would not be usable in Northrend until level 78. In my opinion, flying in Northrend at low levels should be hazardous, not impossible.
Blizzard's primary motive in disabling flying mounts is to prevent players from skipping content. One should not be able to just take off at the starting zones and fly straight off to Icecrown Glacier. But banning flying mounts altogether is throwing out the baby with the bathwater. Just like having T6/T7/Arena gear will give you an advantage while leveling, so should a flying mount give you some benefit, especially the epic ones.
Fortunately, there are ways to limit the advantage gained from flying mounts without banning them altogether. Here's a few suggestions:
- Liberal amounts of air defense, especially around points of interest. Just like in Warcraft 3, flying over a fortified Scourge base alone should be fatal. Some sort of homing attacks that could only be avoided by flying behind obstacles would be ideal. Such as.. ziggurats' energy blasts. The bases should also have gargoyle patrols. This would encourage the players to land some distance away from the base and fight their way in.
- Winds. The usual counter to air defense is to fly beyond it's reach. Winds are a way to prevent players from skipping content by flying over everything. If you rise above the air defense, your mount should slow down and get a fatigue meter for struggling against the freezing winds. Eventually, your mount would lose conciousness and fall. Of course, a skilled player should be able to wake up their mount and regain control before crashing into the ground. Afterwards, your mount would be too weak to fly unless you let it rest for x minutes. For added realism, the strength of the winds should be related to your distance to Icecrown Glacier. The closer you get, the stronger the winds become. And when you finally reach level 78, you can acquire your 375 riding skill and ride the winds unencumbered.
- Air superiority zones. In some zones the airspace should be swarmed with hostile airborne units. For example, the Dragonblight could initially be heavily patrolled by blue dragons. Those developers who designed the Netherwing Ledge races, you know what to do. You would be better off just moving along the ground to avoid attention. Later on you would so some quests for Dalaran to cull the numbers of dragons and gain temporary air superiority. Or smack some sense into Malygos to turn blue dragons neutral.