This seems to be a straightforward way to implement a LFG system in game with tools that already exist. A party leader puts in a service requisition into the auction house for people to join his party for a dungeon, or campaign event. A similar approach could be used for guild finding.
I would also add a feature for player/guild feedback similar to eBay related to the transactions. You would be able to see how much negative/positive feedback a group leader had before you joined. That way 1 you would have some idea of their experience level, and 2 you would know if they had a track record of punting people to add a friend for the reward chest.