I dunno... I think the perfect model would be one where height was more limited than it is now (x yards above any ground surface) and players had means of dismounting other players. That would add some drawback to the benefits, would keep the players near the ground/art/other players, and would prevent 'point yourself in a direction and go afk'. If you wanted to go AFK, take a flight path.
Personally I like the freedom of flying, but it does trivialize the world.