That's a great idea! Just about everybody can drill a small hole to install a cotter pin,
There's no need to keep the towbar and ball in the receiver year 'round, only when towing.
If you're talking to me, we don't leave the ball mount in. If you leave it in for a winter here it doesn't come out again without torching it out. I'm just talking one trip in the salty time of year.
My brother in law thought he was smart and greased the shank all up and thought it would be fine for the winter lol. I asked to borrow the ball mount a couple of months into winter. We tried heating it and using a 10 lb slide hammer / sledge in alternating turns. Nope.