It's not like they have never done it before....

If they could do it in Final Fantasy X in the Omega Ruins...where you had to run around to see this optional dungeon and where you're going......why can't they do it here?

If Final Fantasy XII and Final Fantasy XIII-2 had NO maps when you started in an area, and you either had to navigate every corner to get the full map, or buy a map but was greyed out in areas where you haven't explored.....why can't they do it here? FFXIII-2 even had a fragment reward for 100% completion in most areas....

I'm sure they'll come up with something that doesn't unlock the entire region around it when you take one step into the zone. Heck, half of Coerthas will be lit up with a steps away from the aeths then.