Level 8 Air Sweeper Idea

So obviously a stronger wind or longer range for the air sweeper on level 8 if it existed would be too OP, so how about when you upgrade the air sweeper to level 8 it'd have 50 more HP and also shoot out toxic air that would deal around 10 to 15HP damage to air troops in addition to pushing them back? Also if being able to upgrade all air sweepers to level 8 to shoot out toxic wind would be too OP, how about limiting the amount of air sweepers you can upgrade to level 8 to just a single air sweeper? I had this idea on my mind for a little while and I wanted to share it somewhere to see what others think.