Secondary Army

I would like to have the ability to train an entire seperate horde of troops, basically like a standby army. The purpose of this would be to have the option to use either "Army 1" or "Army 2" during a raid. For example, if your primary army is geared for primarily ground assaults and you choose across a base that has weak air defense, you can toggle to select your secondary army comprised of aerial troops. Any thoughts?

I like the idea. Sometimes I find a base with great loot and ZERO air defense, and I'll be so sad because I'm not using my balloon army.