Since I prefer Metol to Phenidone, I've been playing with the idea of using D23 as a sort of stock solution since the required amount of Metol is only .2 grams per liter of Gainer's formula. I plan to make the working solution by starting with 900ml of water, adding 2.0 grams of ascorbic acid, 26.6ml of D23 and 6.0 grams of sodium metaborate, in the form of PMK "B" solution and topping it up to 1.0 liter. I figure that the 100 grams of sodium sulfite in the D23 should preserve the Metol for at least 2 months if stored properly.
I'm basing my idea on Pat Gainer's Vitamin C developers, but trying to eliminate errors in weighing out small quantities of Metol every time. Since I do use D23, I thought that it might make a good stock solution for the Metol, and if I don't like the results from Gainer's developer, I still have D23.
When diluted, there will be less than 3.0 grams of sulfite in the developer compared with none according to Pat's formula. I don't know if that would make a big difference or not, so I'll need to test carefully. When I have the chance, I'll run some BTZS tests with a couple of films and see what happens.
Since I'm not trying to make a developer that works like Xtol this may not be what the OP has in mind. I was just considering an alternative.