Clan Wars ~ Use Oponants Clans Castle?

Okay so here is my idea: In a Clan War, many people are saying the preparation day is too long. I may have a solution. What if, in the last 4 or 5 hours, you will get a notification saying you are able to fill any spaces in the enemies Clan Castle with your 'undercover' troops. You don't get to find out what's in their Clan castle, all the troops do is wait until battle day, then when the other Clan castle troops are triggered, you friendly undercover troop comes out (always at the end) and attacks as if it had just spawned there.

Please comment if you think this will be worthwhile putting in, and if not please do add suggestions!