What I typed out originally was 'People who hate the SadersEveryone vs People who like the Saders' Then I remembered unsigned Seasonal Rugby contracts
Birthday months maybe? Might be quite difficult but if you got people posting their months of birth it might work, or being born with a date bracket (ie. Born between 1st-15th of any month vs 15th-31st of any month)
Asia (including those Rob wont allow to switch) vs North Academy Stingrays XI vs Scotland (OD Match) Just a few I would like to see.