Just a few thoughts.
London, during the war years, had about 450-500 balloons deployed. During the V-1 offensive against London in '44 about 1,750 balloons from all over Great Britain were amassed around London.
You may need A LOT of balloons.
Generally, the balloons could be flown up to 10K, 8K was common.
Parking a bunch of balloons over a field or town may well prevent the low level 3-plane diving buff phenomenom.
But be wary of unintended consequences. Those cables will also make it very hard for a Jabo to do his work as well. So just how will you take down the field or town?
And will "friendly cable" be ON or OFF? If you run into your country's balloon cable, will it shear your wing as well as your enemy's?