Mike and Jason: Thanks for the encouragement. My original motive for creating a concentrate was to avoid waste because we occasional shooters can't use 5 litres in 6 months. But Kodak's bankruptcy has heated the fire under me. I love XTOL, and want to be certain a proven replacement is available in case Kodak's B&W division is dismantled.
I absolutely do not want to discourage you from this work, because access to a liquid-concentrate long-life XTOL would be fantastic even if it's just a recipe. But I should point out that Xtol-equivalent developers are available from Freestyle under generic brands, though I've not tried them. Personally, I just bought 15 bags of the yellow and I expect they'll last me a decade.