Allow clan members to test a new base of yours before putting it in action. The troops being free and no time to build them when testing a base. Also you would not lose or gain any resources, but only info on how to improve the base. You can do this for both normal and war base.
Ex) have a interface like the Clan Wars setup where you press a clan member and press attack, which takes you to a barrack kind of setup where you enter the spells, and troops you want to use according to the lvl of your campfires and spell factories and barracks. When the person is ready, they press attack to test the persons base. Once finished the person gets a notification like they were attacked in a seperate test window than the normal attacks. They can watch it and improve their base

