Bill, thanks for sharing your explanations, and for putting the time into making an illustration. They make perfect sense to me. The detail would be, however, in the actual concentrations. If fix 2 stays below 0.5g/l of silver, and fix 1 below 2g/l, ideally below 1.8g/l, always, and with no significant, gradual buildup of iodide, or pollutants that reduce fixer's efficiency and effectiveness—as far as I know that is part of the reason Kodak's two-bath system requires you to throw out the second bath every 5th rotation—then, I think the system would work. I realise, that Ilford publish replenishment data for their Rapid Fix, however, I thought it was designed for a system with silver recovery, rather than a system that works on the gradual carry-out alone.
Have you practiced this approach? Did you gather data on residual silver and thiosulfate compounds left in paper? Other than that, I wonder if it would be convenient enough to replace the existing approaches, but that is not the point—we are discussing the idea itself, after all, at the moment.
I will do more thinking, and I will post again. For now, I am (happily) stuck in the darkroom for another week, then travelling for three more. Thank you for taking the time to explain your thoughts.