Clan War - Prep day - clan attack mode
In order to test out your war base during prep day, members of your clan should have the ability to attack any other base within your own clan. That would enable your clan to actively test out the defensive strategy of each base in the clan against different attacks. At the moment clan chat and advice is the only way to fine tune your bases in prep day but actively testing the base with your own armies would provide a better forum for discussing strategies within your clan. Also it gives you the opportunity to gain kudos amongst your clanmates.
It would work the same way it does for enemy attacks in that you would need to cook your army / spells to take into the battle and have cc filled by clan mates. Pick a base on your own clans side of the war map and attack. No points or loot would need to be included it would only be used as an indicator to see how many stars you would realistically attain against each base layout.
N.B. This functionality should only be available outside of war time or before the clan opponents & bases are known. This would prevent any cloning of enemy bases to give you an advantage in war.
Either prep day should be split into 2 parts.
Defensive strategy: 8hrs testing your own clans defences before enemy clan name and base layout is revealed, and then the remainder of prep day is as it is now.
Or the functionality should be enabled after war finishes and before the next one starts. Clan members on the last war map would stay there with the original war cc troops and bases could be edited / cc troops replaced and any member of the clan can try attacking them to identify weaknesses and provide feedback