Please impose a minimum wait time of 15 minutes in the queue before being matched to opponents, and give each alliance leader the option to EXIT the waiting queue. This would at least provide a brief grace period in which to withdraw any war declaration that may have been accidentally or impetuously set in motion.
You have insisted on allowing just any member of an alliance to declare war. You have created transparency so that the declarer is revealed in chat. (This information should go on the war screen and not get buried in chat, by the way.) Now give the leader a temporary opportunity to reverse that.