Reading this reminded me of a post I made a few months ago about the maps, and as someone who really likes open-world dungeons, this is sort of relevant, haha.
I realize it would mean drastically altering the maps we have now (as well as making brand new ones), but it would really open up the possibility of more open world content. Or, at the very least, increase the amount of exploration we can do. As has been said in other threads, the world we have right now lacks teeth. The strongest regular mobs we have are level 49 Beastmen and level 50 Water Sprites--not the most threatening enemies when you run across them, even at iLvl50.I think it's more an issue of verticality than map size. You can make your maps as large as you please, but at the end of the day if it's overall design is flat, then you're not properly utilizing all of the space you have to work with. Coerthas Central Highlands does this better than any other map in the game, although it could certainly be expanded upon. The caves connecting the two fissures at Witchdrop is a perfect example of this, and the caves on the east side of the map, as well, since you can only enter from one side (if memory serves), and then drop down from the other end. Then you've got the climb at Snowcloak, the chasm at Whitebrim, and the crater at the Boulder Downs. Rather than make use of what's at eye level, you can actually move up and down at certain points on the map to either get a better vantage, fight different monsters, or fulfill a quest (although that last one is standard fare, no offense, devs!).
Could you imagine jumping into the pit outside of Buscaroon's Druthers to enter the Gelmorra ruins, running through a maze of tunnels and the ruins of a forgotten city, until you come out at the North Shroud? Or falling through a sandpit in the Sagolii Desert, entering a vast cavern filled with high level monsters and environmental hazards, and journeying through that until you come out at Northern Thanalan? I'd love to see implementation of areas like this in the game because it would really add to the exploration.
So why not throw in these 'open world dungeons'? No mini-map display for them, just a place where the player can run around in, get lost, find themselves face to face with dangerous beasts, discover rare gathering nodes, and maybe even give even players in iLvl90 a bit of tension by throwing in the occasional Lvl100 monster? It would be pretty crazy to be walking around the Gelmorra Ruins when you see a collapsed building, enter it, and find a new type of Valefor chilling inside with a dozen souped-up Vodoriga's around it. Next thing you know you're running outside and either everyone's up and escaping from the area, or they're all fighting tooth and nail to take 'em down. Now that the monster's dead, you go back into the house and an cellar door has become interactable, taking you down into a cave below the house, and you just keep going...
Implementing open world dungeons that are massive, rewarding in both challenge and items, as well as just plain fun to go around with your friends; that's what I'd like to see added. Plus, it would add a bit of a 'Metroidvania" style to the world, having the dungeons connected at multiple points to multiple maps.