How about a single player tournament
Have you considered a single player tournament? Since the whole idea behind this and other games is to make money for the developers, players would pay in green gems to participate in a tournament. Say 10 gems to attack or buy 1 new red gem just for this tournament. Best scores would win gems.
To keep things fair, everyone attacks the same base. How about a completely maxed out base to attack and see who really has attacking skills? If you allow players to watch replays before attacking, then you could have same base plans, but move giant bombs and teslas to keep things interesting and players would not know where they were. You could either have a designated amount of troops that everyone uses that would all be the same, or let player choose his own like we do now. He would have an allotment of say 240 troops and all troops would be available to choose from.