Team registrations
Team registrations would allow development of leagues and a lot of fun.
A lot of known players play 0ad in teams everyday. In fact, most of the fun games are played in teams. By allowing players to register in teams with a condition that the players in the team each must have at least 1300 ratings and having played at least 100 1v1 games with known players, across 3 months, would reduce duplicate account creation.
There will be a value to maintain your 1v1 ratings and a price on account names. This would allow development of good teams and balanced, fun multiplayer games.
Team ratings
When team registrations are curated, the games would be played without disruption, rage quits, etc. This would give importance to team ratings. An algorithm must be developed to assign team ratings. In particular, ratings must decline if the team does not play for long time. (This should be the case even with 1v1 games.)