[tobz]

Partially valid: having different diameter tires can lead to lash or noise in the drivetrain, but that extra noise/stress depends on the diameter difference. You're not going to HAVE to buy all new tires if you have a blowout and need a new one. Your drivetrain won't explode if you put on a new tire with three used ones. Decent tire shops are able to shave tires to match the rest of the set if there's a big difference.

[chadgeidel]

Also, I don't see anything physically connecting the front and rear tires - this is where much of the drivetrain wear comes from on AWD/4WD vehicles.