All the ideas and info are in the other thread: "A new MVP" which went from adding some custom MVP to making a large elite-type quest out of it.
Basically, There would be a new world (credit to Amitsu) in which you'd do the quest. You can only enter this world (via an NPC somewhere) if you're an Elite. For the maps of this world I'm sure someone here has the ability to customize existing maps to make them looked ruined or destroyed.
You do certain steps of the quest alone until a certain point, when you'll need a party of players at the same stage as you to continue into a sealed dungeon to defeat a series of obstacles.
At the end there is a final custom boss (which is in the making), which will be extremely difficult to defeat. And parties will need a specific amount of members to enter the MVP's map, which will hopefully be fully custom as well. The map will not be warpable, so if you die you need to be resed. And if you leave the map you can't come back. (something like that)
And the MVP will drop x amount of stuff that party members will then present to an NPC and then they become a forsaken Dragoon, with some sort of perk.