I suspect some of the questions you have may be much studied scientifically, by soil scientists, civil engineers, etc. They may already have identified paradigms, testing procedures, etc.. in fact, I think there is every possibility that the standards you are looking for are already out there, and could be applied to the ceramic arts without too much difficulty.
I for one am wholly in favour of some standards. Convincing clay manufacturers to accept them or potters to use them may be another matter if this thread is any indication. If they get a critical mass of acceptance amongst potters, then manufacturers might just roll over. But it will take work to show why and how such measures are useful. Time to don your missionary garb...
The whole discussion in this thread about force to move clay, density, mass, particle size, etc. is very familiar from discussions I have seen on shear stress in soils.
See the following link, and also references to Tresca (the "father" of plasticity science) within it.