I think it would be beneficial to everyone if they were able to attack their clan mates. It's just for strategic practice and constructive criticism. Also when you do attack, when its over you keep the troops you used and you dont lose trophies or loot.
This is like the "attack your own base" suggestion that was nixed. Same concept. If you wanted to revenge a base and wanted to try different strategies, this could be abused. I doubt this will be added.
