They've certainly gone for the extreme side of changing the law. I wonder if they'll reconsider this very soon.
My thought the other day was this: give batsmen the option of a runner but if they take it, then they have to sit out the next match. That would flush out the 'fakers' who are just cramping up from the guys who actually can't run due to a proper injury. So you'd have to weigh up the severity of the injury against how much they need the player to contribute, in that match and in the series. Eg. under that rule, SA might have decided Kallis could bat well enough without a runner, just to give them the option of picking him for Perth. As it turned out, that's what happened, and that's what SHOULD be happening, not just trotting out a runner for everything, or the other extreme of outlawing them altogether.