How would I set up the brawling quest for an NPC? I need to make a separate one, I think, for a few reasons:

1. The NPC is not fighting you for a bet. You make fun of him, the brawl starts, and when you win you get a custom item as a reward rather than money.
2. You can only brawl him with certain conditions (a certain quest stage).

Really, I just need you to be able to fight the NPC (started by a dialogue option), without others freaking out when you fight, and when they go down on one knee, end the brawl and get a unique item through the dialogue (all of the dialogue would be unique as well). I can probably figure out some aspects of this but I was hoping there might be someone more knowledgeable than I who knows how to do this without a bunch of trial and error.