If Square were to make a dungeon like this, there would have to be a few rules;

1. The dungeon would have to have sections that save your state. Each section would take 30 minutes to complete. If you leave in the third section, next time you queue up for the dungeon you start at that section. This is so that people can complete the dungeon on their own time. This may not be necessary for pre mades, but for PUGs, 2 hours is too long to finish in one sitting.

2. The dungeon would not appear on roulettes. This dungeon would have to be picked intentionally.

3. The dungeon would also not be needed for farming. Perhaps you gain a currency for each section, and you trade those currencies for cosmetics, such as clothing, minions, mounts, furniture, etc... Perhaps add different effects to your weapons/armor.