Just a quick idea!
Let's say a Cannon is 50% detroyed, it should deal 50% the damage it normally would. If a X-Bow is has 75% of its basic HP left, it would only deal 75% of its original damage. If an Archer Tower is 90% destroyed it would only deal 10% its original DPS.
You all get the drill here!
Ofc this would require a huge balance patch...
However, the idea makes sense, doesn't it? :)

