Very interesting and fantastic suggestion. PvP 1v1, 2v2 and Guild. Your Guild could be up to 5 team members. An individual would have to 'create' the guild and there would be options to... 1. Join if MMR >1900 (guild owner variable), 2. application, 3. recruiting (all of which would be variables & could only be modified by creator/owner of the guild), 4. Remove team member etc... The people in this guild would do 1v1 and their aggregate score could constitute a guild MMR. Very cool indeed - if that is what you envision. It would add a new spice to the game. If not now, maybe DQ2 will have that capability... Maybe a reward system for guild rankings every week... Rewards could change based on what devs push. 1st place guild team could get 20 obsidian, 2 elixer and 5 boosts etc.
Edit: Being in a guild could/should also cause a guild to become banned if a team member cheated.
The fight could also be a ten person melee...