Training idea.

How about creating a inner-clan training arena. Allow clanmates within their clan to attack other members of their clan for training purposes. With no resource loss and no cost to the player. Basically allow clanmates to practice different attacking styles on each other without have to spend resources to rebuild their armies. This will incourage weaker members who constantly lose in battle and get discouraged and quit the game. My clan has lost six good members in the past month due to mismatched wars and frustrated members. Each member desided to quit the game.

Like you said, this allows players to practise attacking with no cost, so it's not going to happen. :)