Good points. My feeling is that once a few spindle and bearing sets are tested (you don't need a K&C machine to do this, just a fixture) a common stiffness
in camber and steer will address all the concerns. This generally works because the cars are just about the same weight, same loads, same architecture,
so bearing selection and spindle strength are probably pretty close in the field. Some makes, brands and assemblies will sort out as better than others, just like steering gears.
As for wheels, a set of gentle tests of the same tire at TIRF on all the wheels of a common rim diameter will show the cast of characters.
I'd rather see this than one more shot at a bunch of tires that will probably be close to previous tests.
And run camber sweeps instead of slip sweeps. That's where all the questions seem to be coming from. Too bad if your tire model fitting program pukes.