) Regarding the Halacha of 4 inches, the Rabbonim should come out with a uniform standard, whether it’s 4 or 3 or whatever.”
There IS a standard of halacha already. The skirt should cover the knees, even when the woman is sitting down (presumably this especially includes when she gets in and out of a vehicle or climbs up the stairs). For each woman that may be a different number and also depend on the style of skirt or dress she is wearing.