Anyone McCain picked would be exposed to attacks, with a *few* third party malcontents here joining in. The pick is never going to be perfect, but why don't you tell us your pick and why it would help McCain. Also realize that your hypothetical pick won't go through the media wringer.
You have a point. Looking down the list of possibilities, I see many who are not conservative enough to mobilize the base, and some who have no interest in running with McCain.
He could have picked Huntsman, for example, the governor of Utah, who had experience in Reagan's White House staff before being ambassador to Singapore under GHWBush. He also did missonary work in Taiwan and speaks fluent Mandarin Chinese.
But, his dad was a billionaire, he's a Mormon who isn't Romney, and he has no vagina, so I'm not sure who would be excited by the pick.