Only problem I have with suggestions like this is that, well... Eorzea isn't some new frontier. It makes sense for civilization to be spread across Eorzea. Maps like 1.0s and XIs made absolutely no sense to me; you have a world people have lived in for decades, yet the most civilization you see outside the city gates are small outposts and the occasional small settlement. There was zero sense people traveled between cities in either world. ARR has done a phenomenal job in that regard.
That's not to say I wouldn't want to see larger, isolated areas. I just want them to make sense. Something like the Tavnazia zones in XI for example, that made sense. It was cut off from civilization for years and the only settlement belonged to a small group of survivors. Somewhere like Coerthas Western Highlands could mirror that. As can various other locations, like Sagoli Desert. Areas like Tavnazia are great, but sticking them everywhere just breaks immersion; there should be infrastructure, settlements, and patrolled routes between Ul'dah and Gridania. Given how long people have been in Eorzea, there really should be in all but the most inhospitable of areas.
Gods yes... Even the birds we do have in ARR, is it just me or are the flying unnaturally slowly? Every time I see them I can't help but think "That's a set piece they've got moving to slow", and it completely breaks the immersion. Not helped by the fact that there are so few birds around.
This I don't get why they haven't done from the start. The open world dungeons in 1.x were perfectly serviceable for ARR. Slap some FATE bosses around, keep the Key/Coffer system, make the rewards similar to dungeons and perhaps slap a lockout similar to virtually everything to prevent mass overcrowding a'la Hunts. I'm hoping the various locked off gates in Beast tribe territories eventually give us some open world content.
Also, some of the dungeons are absolutely amazing zones, and I feel the world could be made a lot larger if you just turn some of them into open world zones after their completion. This could add more open world areas easily, as well as providing a few new areas for side quests, Hunts and gathering, to name a few. It wouldn't be exactly the same as open world dungeons, but it would go a ways to making the world seem larger; you complete an instance and then that instance becomes part of the open world. That just makes sense to me. The implementation of hard mode dungeons kind of destroys that possibility though, I suppose.
One thing I would like to pass on to Junichi Murata; Revenant's Toll is absolutely great. Seeing that settlement build over time is one of the highlights of this game. I'd love to see the maps evolve like that in the future, even if it's just slightly. When we move onto dealing with Ishgard and the Dragons, it would be absolutely amazing to see the damage and repairs being carried out, for example.