Train an army specific for War, but separate from normal base army

This would be a fantastic addition in my opinion. Sometimes I need to attack for elixir to train the rest of my war army, which I can't do because what I already have occupies my camps already. It would be fantastic if Supercell would add an option to have your army train for war or "not-war". Of course, the war army should not be able to be used for anything aside from war, as two pre-trained armies would be a bit overpowered, and the non-war army should not be allowed for war. Thanks for any comments, feedback, and consideration.