They first need to change their mindset, which is removal of all variety. That's why swimming and diving are nigh useless once you unlock flying. I'm surprised they actually added spearfishing...but that's content only for 10 levels of 1 job. Which is also the least interactive job in the entire game (at least till that point).

Once they change their mindset, they can make actual content for flying and swimming/diving. Underwater combat would be interesting too, even if it was utilizing simplified mechanics and specially made, limited skills.

Once that's done, THEN they thinking of other mobility updates would have any sense to it.

Why?! Because they'll add climbing. And what?! You'll be able to use it only on new maps, that's what. Suddenly your character which can climb vertical hills is unable to get on top of a boulder that's just slightly higher than it...Why?! Because the A Realm Reborn maps aren't prepared for it. Because you could unlock flying too easily and too quickly. Because they'll find whatever stupid excuse to not do that (and there is actually technical excuse for that, as the system would require making "climbable" terrain, where currently there is a "no entry" terrain).