I would love to see alliance member's and friend's replays. It could be used to teach, learn, understand, coach and plenty more. Would be nice to see this added.
This is my #1 most wanted feature, by far, and I know many who feel the same. Everyone would learn sooo much more from each other, so quickly, if we could share attacks. It's also difficult to see alliance wars ever happening without the option to view each other's battles. And it's easier to brag about your awesome attack with video proof! :-D