The realistic solution is to use the solo duty asset the game already posess to allow players the one time completion of a story quest. The game has already proven numerous times that it can make use of an existing area, limit it with zone markers and use AI npcs to assist the player to complete them. This allows players to seamlessly go through msq without having to wait for a group, it allows cutscenes during msq to be viewed at the players leisure however they see fit and everything is scaled accordingly. Once the solo duty is completed, like all solo duties in the game for msq and class quest, it cannot be redone.