Along the same lines I loved the Serious Sam solution to piracy. They let you play but spawned an invincible enemy occasionally to ruin the experience.
https://www.thesixthaxis.com/2011/12/08/how-to-get-rid-of-th...
https://www.thesixthaxis.com/2011/12/08/how-to-get-rid-of-th...
This happened a few times at LAN parties to my friends, some of whome gave each other the game by copying the install directory across. Took us a while to work out what the hell was happening.
I remember in Settlers 2 or something (before Ubisoft ruined it) the iron smelter was producing pigs in pirated versions.
However, it wasn't extremely good at detecting them leading to pissed off legit players.