If it's not too late in the game, I think it would be fun to have a random option in the Choose Opponents screen. For instance, to be able to randomize which races will be in the game, as well as perhaps randomize the difficulty of each race. IMO that would really add to the replayability factor and make things interesting.
Apologies if this suggestion has been made before. The lack of a search button in the forums makes it difficult to determine if it has.