You put your finger on the reason I asked TM about the methodology he used. You are correct that Marco bases his measurements on the water, and until I got used to that fact I sometimes used too much starter in my 00 doughs that were based on Marco's dough formulation. As it so happens, in TM's case the 4% Camaldoli as a percent of flour is just a bit over the 5% max as a percent of water that Marco recommends (his range is 1-5% by weight of water). Like you, I have built my spreadsheet in the conventional manner and have gotten used to it. I think your recommendation works well when there are only a few ingredients involved, namely, flour, water, yeast/starter and salt. However, I recently worked on a dough formulation that used nine different ingredients. I found that the standard baker's percent system worked well, and it might have been confusing to the people for whom I did the number crunching if I based everything on the water. For me, the answer may be to have two spreadsheets--yours (or one like it) and the standard one.