I was planning to write something about this myself, glad you’ve brought it up :>
I think this is a fun idea, one I’ve played with myself, but it might be a little trickier to do this right than at first glance. A lot of players choose their mounts because of what they look like, and a lot of those same players would also want to choose what is perceived to be the ‘best’ mount. Giving mounts traits that make them better than others means everyone will be using those for this and that purpose, think back to how everyone used to ride on the water strider mounts before mount equipment replaced that. If, for instance, it turns out dragons are just the best mounts, now everyone are riding dragons. Mount types would have to be designed with that in mind.
While I do like mount types, I think it would be even better to expand on an existing mount system that is rather lackluster: mount equipment. First, I would make mount equipment fit to individual mounts rather than all of them, or perhaps having the option to give individual mounts the option to wear a piece of mount equipment that would override the one that applies to everyone - or just have the ability to unequip that mount equipment and move it to another mount without destroying it. This would open up for being much more creative with said mount equipment, since you can have multiple different types of it. It could even be used in tandem with mount types.
Generally, I like the idea of having several different mounts that you would use in different situations. I used to have one mount I would use for traveling on the ground, a flying mount for flying areas, and the water strider in case I had to run over some water. Now I’m down to the former two, which fits much neater into my macros, but I feel like I have lost something. It’s cool when you have different mounts that you can use for different situations, they feel like useful tools that you can use to enhance your gameplay.
I would be pretty happy to see more content that you can only access with flying! Hidden areas or even quests that require you to fly around would be pretty neat. My personal favourite moment of flying being used for gameplay was leveling during Wrath of the Lich King, and reaching the Storm Peaks for the first time. With the ground mount, you felt so small in the face of those impossibly tall mountains, only able to access a tiny portion of the zone - and then you’re given the reins to your flying mount, finally being able to conquer the verticality of the zone… a feeling I think will be really hard to recapture nowadays, sadly!
I think a big problem with flying as a tool for gameplay, is that it is really, really powerful and it can be very hard to design content around it. Making content that requires flying doesn’t fix the problem that content that does not require flying feels trivialised because of it - which in my opinion is a much bigger problem.
Flying does not just allow you to get somewhere faster, it also allows you to skip a lot of content, avoid combat and world PvP, for druids it can even allow you to pick up items without going out of flight form to escape instantly in case you aggro an enemy. Restricting flying is actually a good way to combat that problem, although, it can be done without removing the ability to fly outright until you have unlocked it.
A really simple idea brought to my attention after I wrote about this in another thread (9.2 and the increased flying grind) would be to simply design more indoor areas out in the open world; areas where you can’t just fly your way in and avoid everything. You can still fly to and away from the area, but you are going to have to get down on the ground and actually experience the content as it were. Other ideas is to restrict flying in certain areas by adding threats in the air; this already exists in the game, as some areas will dismount or damage you if you linger for too long and/or don’t dodge the attack. I’m sure there are other ways to do this that I haven’t thought about, too.
I’m of the opinion that the problem is twofold; it’s not just level design that doesn’t take flying into consideration which is a problem, it’s that flying is just too good. Nerf flying!.. I’m joking. Sorta. I wrote in the other post I linked above that:
I understand why no one wants to change this system as it exists now, though, because people might find it jarring to have this insanely convenient system made more complicated.
And I would be pretty upset if I read in the patch notes that flying was just straight up nerfed, myself, and I’m here advocating to change the system - if it’s a tough sell to me, it’s a really hard sell to people who want no changes. It would be a really unpopular decision to change how flying works right now, even if I think that is probably going to be healthier for the game in the long run.
I’m actually really interested in hearing devs’ thoughts about flying: what are the challenges with flying, how does it influence level design, have any changes ever been considered to the system?