It seems to me you've just articulated a fairly powerful argument against this happening.
I'm having a hard time seeing what an acquisition would accomplish for Apple that a nice fat contract could not for much cheaper. It's not as if chip manufacturers tell customers the size of Apple to just get lost if they need a custom chip for some purpose. A "nice fat contract" negotiation would look somewhat similar to acquisition negotiations for rumor mill purposes, too.
I'm having a hard time seeing what an acquisition would accomplish for Apple that a nice fat contract could not for much cheaper. It's not as if chip manufacturers tell customers the size of Apple to just get lost if they need a custom chip for some purpose. A "nice fat contract" negotiation would look somewhat similar to acquisition negotiations for rumor mill purposes, too.