What about a flying spell? Flying spell can help ground troops to fly just like jump spell but ground defences like canon and mortars can not attack them and also air defense. But archer and wizard tower can. Archers and wizards can attack defences or any target from air because off their range. It should be dark elixir spell with small radius and it affects around 4sec. on lvl1 cost around 100 d.e. Lvl1 and take 18 mins to produce.

