Actually, if you think about it this way: It shouldn't really be a rank but in general some sort of tags for playing the game could be added. While you're playing that game mode and you say something in the chat, a tag infront of your name related to the game would appear. This would be based off your stats, such as kills, wins, playtime ect.
Hard for me to drop all the possible names of tags that could be added but in general this would just be a fun thing and could also motivate players to gain something else than just wins, and this would be possible for anyone. Nothing special would be given, only a fancy little tag.