Hi there.
I was thinking of something along the lines of the “qualification” challenge for the CTP (from OffSec) course.
People who have done it should know what I mean. If you haven’t you can go and try to sign up for the course and see what it needs you to do for it.
Additionally, the shellcode could display a warning message or something of sorts when simply run. Just to discourage people from running random executables.
Possibly even a full RE section?