The "proprietary" issue makes sense in that Gillette is, after, all a business. But a proprietary blade would entail investing in a brand new razor format. I'm not saying that wouldn't happen; it's just that there's not much advantage to the shaver to use an exclusive blade if he can something cheaper elsewhere.Good observation.
I think Gillette would try to undercut the market, and rely on performance and reputation. Sell s precision plastic razor that looks and performs brilliantly. Gillette already has the market edge on blades. The new Gillette razors would cost pennies to make.