My biggest draw to flying was being able to get over a hill or around an obstacle that was pissing me off.
If the quest was 5 feet away but I had to go all the way around a mountain I was pretty agitated by it.
So I was curious if an introduction of mounts that could scale terrain would be a good idea.
They'd function like ground mounts only they would be able to climb terrain that a ground mount or player couldn't.
However to prevent this from being abused it would have a fatigue bar preventing the player from climbing difficult terrain for more than a few seconds.
Regular mounts would have X timer on their fatigue bar.
Epic mounts would have X+Y timer on their fatigue bar.
This would help ease my frustrations of no flying while still staying true to the no flying in game now. It also would avoid blizzards concern of players pointing in a direction and afking until destination with the fatigue bar. Only being able to climb while you have it and having to wait for it to recharge until you can climb again, So if you hit a wall to tall. you'd keep sliding down it until you came back to find your character stuck.
I'll admit it's not flying but it could be an alternative that might tend to some pro flyer's concerns.