Need to address the Eureka in the room.

[Physic]

Step 1) Open World Zone Instances
Step 2) Player Limit on Open World Instances
Step 3) ???????
Step 4) PROFIT

Just being realistic here >.>

Yes, you devalue things like Ixion spawns and Hunts because you no longer enable thousands of players to all leave their preferred AFK City to all jump in on a spawn, but to be honest the way that things like S Ranks and Ixion spawn are not particularly well implemented anyway.

Meanwhile, you'd open up the possibilities of you know, actually creating open worlds that matter, by having FATEs, chains, A Rank and B Rank hunts, Raid FATEs and the like actually being valued. Without having to shove all this actually worthwhile open world stuff into a separate Eureka zone while leaving the actual open world to rot when it's only ever used by people doing MSQ or gathering (Outside an S Rank/Ixion spawn when everyone flocks to the same place and crashes servers >.>)

server based open world content will fail due to different server populations/time zones and interests. Open world needs to be like mega server/cross world.