These are two different discussions being cobbled together.
1) is it a good business model? Maybe in a very limited, narrow market. As @TwiceHorn said - bait shop, rural hardware store, some other appropriate place as a gimmick. That’s discussion A
2) Is it going to be abused by criminal element?
All these scenarios of mannequin heads and hackers seem to miss the key element- No one is stopping the criminal element from walking in and buying a box of shell manually anyway.
Your scenarios are akin to hardening security around copper tubing sales to prevent Cletus from moonshining to get his booze fix. He doesn’t need to build a still. He can walk next door and buy his bottle from Jacks liquor, or ask his brother to. Ammunition is not some rare, guarded commodity requiring a Dirty Dirty Dozen or Oceans 11 plot to acquire. You’re over complicating this.
Do you see organized crime syndicates devising ways to help 17 year olds get lottery tickets from the machines in grocery stores? No - not necessary- just buy them or send someone to buy face to face.