My opinion, for what it's worth, is that none of the reasons you give provide a compelling argument for what you want to do. I'm sure many of us here have .222's and .223's (I do) and never have had a problem keeping ammunition sorted out. The longer neck on .222 is very obvious (at least to me.) There would be no appreciable performance gain and I'm almost sure bullets heavier than 55 grains would be out of the picture. It's a nice gun, a little unusual, leave it be.
