Since the game allows it allready in custom mode, there is no reason why mirror matchup should be impossible in standard automatch.
All i m saying is: Dont have it as default but as possibility with a checkbox.
They can include a filter-checkbox that says "mirror matchup" so those that really want to play it can choose to do so.
1. Players will get more aware of what part of their fav. faction is trully OP before they start complaining.
2. Matchup search time will be faster.
3. More ways to play the same game.
4. If nothing i would really love to see UKF vs UKF sim city fight
Relic can learn a lot from SC2.