That Special weapon function is Mind controlling All the chickens in the battlefield , They will now fight in your side and you wont be affected by their shots but they can be destroyble by the other enemies chickens , and they will back in their minds after you pass five waves so you need to be careful after they are back , they will go anywhere , And the Shape of the Special weapon will be A Wifi like that
Maybe an item called: Traitor. The shock wave from the Spacecraft hits nearby chickens and will fight for you for a certain period of time. Do you like my version of your idea?
So you could skip an entire wave, controlling ALL of the chicken and bring them to fight with you for 5 waves and at the next wave you will face that wave and the first wave combined? Sounds op, but really backstabbing later.
You can skip any entire wave by the weapon , but be sure how many chickens you will mind control becuase they will back in their minds after five waves as i said , they will go anywhere , and you might be died in this case