"We all know the rears wear out faster than the fronts. If you don't replace the fronts the same time as the rears, even if I replace the rears with the same tire type, since they would have 100% tread and the fronts would have (say, 75%), wouldn't this be (in theory) the same as mixing tires? "
Not quite, the fronts still have the same tread pattern, sidewall stiffness, rubber compound and such. I can go through three+ sets of rears to a set of fronts. Every time a new set of rears (PS2's) go on the car the whole car feels nice and sticky again....
Ed
