New form of fighting - Water based.
To the left of your Clash of Clans Base there is water. Why not put it to some good use instead of decoration.
Alongside the land combat, why not introduce some naval combat, by which (similar to clan wars) clans verse other clans in an attempt to destroy the others fleet and naval base.
To accompany this, players could also create their own naval bases similar to the ones on land. Again these bases can be upgraded and defences consist of torpeedo's, missile launchers and water mines.
Troops could consist of fire boats (which explode on impact - aka wall breakers), Cruisers (the tanks of the sea - aka Giants), and aircraft carriers which release balloons at a low level, then minions, then finally dragons. And keeping the game fantasy based, why not have wizard boats, and spells could be sea monsters which come onto the screen and cause damage.
Instead of a barbarian king, why not have a sea monster to defend your base?
Just an Idea, let me know what you think :)
Luxsill