Easyjet already uses drones for airplane inspection at Gatwick and Paris.
There are other uses.
As far as the shotguns, catapult, paintball - they are inefficient and prohibited for city limits in some places. If a drone is that close for you to use any of those you are better off with a bog standard pressure washer and a bottle of paint or dye instead of the detergent.
The issue with all of them is - by the time you got to one of them the drone is gone. So you are better off with passive defences. Privacy foil for windows is about 5£ a meter and takes approx 15 min per window to install. I got it on most windows already to reduce glare and heat in the summer.