All very interesting reading, some valid poins and observations
However, here is my little input
Firstly, tread and tread pattern are primarily there to displace water, its the compound of the tyre that is the key factor
Obviously a lot will depend of how/where you drive the car
I still own and have rode many high performance motorbikes both on the road and most uk circuits
Would I mix tyres on the track on my bike, nope, on the road, yep, done it many a time, by mixing tyres I mean brands, as long as they have a similar compound there is no problem
Rob