recharge loot in goblin bases
I enjoy re-attacking the higher level goblin bases with various troop combinations to see how powerful different armies are, but spending the time and elixer to raise an army and defeating a base to receive 0 reward is a bit of a downer.
If the goblin bases slowly recharged their loot (as if they had a resource collector) it would make re-playing the goblin bases more fun. It wouldn't need to be a particularly fast recharge, nothing high enough to draw attention away from player-vs-player, but just any amount of recharge at all would make re-play more rewarding.