I do see where you are coming from, and it is possible if we get a really solid conservative nominee that they may go for some "moderate" the media will like to shore up the mushy middle, but a pro-abortion candidate is just unacceptable. Alienating social conservatives would be a big mistake.
Personally, I am thinking top choices for a VP nominee would probably be someone like Rubio or perhaps Pawlenty (assuming he doesn't win the nomination). Both could help us win important states, and both can probably appeal to independents (Rubio brings in Hispanics too).
I see a couple of problems with this:
There are no "moderates". There are conservatives, leftists, and also uninformed and thus somewhat confused conservatives and leftists. We need to explain conservatism to everyone with the confident expectation that most Americans are conservatives.
The media will absolutely excoriate our ticket no matter who is on it.
Hmmm, interesting. I may be overemphasising the NE-establishment-moderate mollifying character of the VP choice, but neither of those seem to have enough of it.
OTOH none of the candidates I think of, like Romney or Rudy, who do have that quality can bring in a single electoral vote.