That is a really good idea. My first thought was basically start with the tree, a drone's natural enemy, and amplify the stuff that makes it so dangerous to a drone - tiny sticks that are hard to see. Fishing line would pretty much accomplish that.

I was thinking along these lines, but with more of a BallonFest '89 flavour to it

https://en.wikipedia.org/wiki/Balloonfest_%2786

Military bases in hostile territory may have to be surrounded and covered over by chain-link fence material on telephone poles.

Kevlar thread. Less frequent replacement needed.

This does not help against attacks that are already being done[1]: Attach grenade to drive, fly over target, release grenade.

[1] https://www.popularmechanics.com/military/weapons/news/a2751...