The roguelike dungeon gave me a idea and just wanted to repost this. With some changes. Hopefully it would be considered.
Make a door that throws you to a randomly selected existing quest up to your level or the leaders level.
The only hard coding they would have to contend with is making sure the whole party can do the quest or just keep it to Free to play quests only. Or the only way a Free to Play player can enter a Pay to Play area (without paying) in this way if it did land up in a Pay to Play quest.
The random door can land you in a random party in a random quest with a random difficultly level.
Lets say if you are level 15 and enter this door (you could choose the difficulty and if you wanted a random party) of the quest but would not know nothing more including quest name and when you go inside you could land up in heyton's quest (in korthos) or the wizard king (in the demon sands).