Summoner DarkHaitsu independently came up with a Factions-esque idea, and has posted a rather pretty GD thread on the topic, including some nifty artwork. I’ve posted one example above.
Here’s the link: Faction wars (GD)
And here’s the Boards Beta thread: Faction wars (Boards)
I encourage you to go chat it up. These threads are both teeming with people going “wow, I’d love to play a game mode like this!” who are apparently unaware of Factions.