I think this is a brilliant idea. “Snub” made a ball turning tool and used a 4-jaw chuck as the base. He says it works perfectly and leaves an almost perfect finish. I don’t doubt him because of the weight and rigidity of the chuck and the large bearing he used as a pivot. His design also looks like it is quick and easy to make. Notice that he didn’t make a holder for the carbide insert. Instead took an existing holder and drilled it so he could bolt it to a piece of steel.
Unfortunately, you can’t use Snub’s idea if you have a small lathe. It would definitely be too tall for a 7x mini-lathe, and I don’t think it will work on my 8×12 even if I use a shorter 3-jaw chuck and somehow directly mount it on the ways.