Balloon Bombers also scout the enemy...
Maybe the balloons troops can lead other troops to a destination. So somehow, you drop a balloon then it does its thing before it gets killed, you drop some other troops within a radius of said balloon and they go in the same path. basically, instead of going right for the resource mines or builder huts, it might head towards something like a cannon (or vice-versa).
Haven;t thought this all the way through, but I was just half-watching a documentary about World War 1, and it was mentioned how the balloons were used... plus, for all intents and purposes, how many people actually use Balloons for anything? Rarely have I seen them used, and in those cases, they are upgraded to the black from red, and used en masse.