Something like this.
A target would be posted at the beginning of each shoot, the shooter downloads it and prints it. Targets would be randomly chosen from informal sources that are available all over the web and would change for every competition. Such as shooting standard bulls one week. Zombies the next week. Psycho killer chickens the week after.
Rifles shoot at 10m and pistols shoot at 5m
Any caliber or sighting system allowed
Self score and post a picture of your target
probably no shooting aids allowed such as jackets, pants, supports etc