This will never happen.
I'm not so sure it will NEVER happen. If there was any evidence Harden could stay healthy as a closer where he is unable to stay healthy as starter, why wouldn't Beane consider it? Sure he's worth more a starter, but he's only valuable if he can actually pitch. Of course, I'm not sure there IS any evidence to suggest this is a viable solution, so it's kind of moot.
The A's really need to take a good long look at their trainers/physical therapists/doctors/etc. Their inability to stay healthy seems slightly more than coincidental.