Improvment That Could Be Made
The best way I can think to improve the game is revise the battle matching system. Base battles on levels not on trophies. There are level 100+ attacking level 60. This is ludicrous there is no incentive to attack anyone if I can sandbag it and attack only people in my trophy level. Then I can be the big fish in the small pond if I adopt this strategy and no one will be able to touch me.
The suggestions in the poll are good I especially like number 4 but the overarching problem is still the battle system.