I don't know exactly how you would get it to work, but I think i woudl be cool if one of the DLC's or some sort of mini-game outside of FNV was the ability to play Caravan versus other people.

My thinking:

Start with a regular deck of cards, as you play you can bet money and you have a ranking. When you get so much money, you can buy additional cards. The ranking system makes it so people who just started have a chance and don't end up playing people who have been playing for a significant portion of time and have finely tuned decks.

http://www.gamesas.com/index.php?/topic/1130187-dlc-suggestions-2/