Really good writeup, makes perfect sense to me.
Its just financially, its not always the practical thing to do thats all.
When i bought my car last year, it had good front tyres, good years I think, but bad rear ones, so before I took delivery, I made sure he replced them, which he did.
However he fitted an avon to one side and a yokohama to the other.... (both had very similar tread pattern so I thought fine)
After 7 months, I damaged one of the fronts, so decided to replace the both as a pair, and got a brand new set of kumho ecstas (which i always found very good on previous cars) However I wasnt getting the grip i was expecting, (maybe now realising i had 3 different makes of tyre) I also lowered the car, and fitted 20mm spacer and had a full laser allignment done.
Having taken the wheels off last week to sell, i noticed the yokohama tyre has worn significantly more than the avon tyre (now i first thought, maybe i need allignment done again) now i realise its having different tyres...
Anyway, I have bought a new set of wheels and reassured (after reading this) that I have bought falkens for all 4 corners! hopefully I will notice the difference in handling now!