Ability to "play-as" a player who left clan during war
Ok, I know this can be exploited without proper controls, but how about giving the leader the ability to assign the remaining attacks of a player who voluntarily left the clan during war? The player who left would still be ineligible for war elsewhere due to the timer. No one would get the bonus loot earned by those attacks. The player assigned as the proxy attacker would have to have been lower in the war list than the departed player (rather than doing something convoluted like having a player use the departed players exact troops/spells/heroes by means of some special proxy attack army screen). Possibly the proxy attacker could get an elixer refund for all troops deployed in the proxy attack.
In order to avoid people becoming hired defensive guns you could make someone ineligible for war if they voluntarily leave three times during the season while in war for the remainder of the season. Heck, we should probably have that rule anyway.