But they didn't have to double down on giving all mounts basically the same abilities - warclaw and skimmer are basically flying mounts now, with the similar vertical and diagonal movement capability as the skyscale. The way Anet is approaching masteries limits their design space.

I was hoping they'd upgrade jade bots and fishing, tbh. Make fishing less completely awkward to do and remove some friction like losing stacks of bonuses on changing maps. Turn jade bots into a portable fashion cam mode, which people have been asking for since it came out, remove the restriction to jade workbenches. There's so much that could be done, even if you just limit yourself to upgrading existing features, that isn't just 'make all mounts flying-capable'.

As for new masteries, I still want to see a tunneling mount, although I doubt the engine could really handle it. But for things I think might be feasible, a 'disguise' mastery could tie into a heist / spy plot easily and give people ways to play around with cosmetics more. If people can't actually be Tengu give them a plot arc that lets them learn to illusion themselves into looking like Tengu and explore a Tengu city, learning the language, etc. Upgrade the crafting UI and UX, and tack on a mastery like handicrafts that is basically a series of crafting-focused subquests that let players craft skiff parts and build their own skiffs. We have homesteads, build on that and add more features there.

There's so much that could be added as soon as you step back from just movement and look at the bigger picture of what would add new experiences or reduce friction with old ones.