Historically a VP doesnt deliver their homestate to the Presidential candidate. I think however that the best triangulation, to use a Clinton term, would be to take Palin as I feel women would see this as the outreach to female Clinton voters who arent just about Party.
My best estimate is that a President moves the numbers 4 points in his home state and 2 points in nearby states, and that a Vice President moves the numbers 2 points in his home state. Gore did o.k. in Tennessee in 2000, and way better than Kerry did in 2004, but not well enough to deliver his home state. But Kerry did make the difference in New Hampshire in 2004. So, in a very close election, the candidate or his running mate might help deliver a particular, crucial state.
The traditional rules for tabbing a Vice President are these:
1.not hurt.
2.balance the ticket, regionally or philosophically (this means McCain has to name a conservative)
3.help in a crucial state.
Your point that Governor Palin can help with a demographic group, cutting across the country, and helping in several potentially crucial states, is a new and interesting consideration.
We Republicans need to appeal to women and to Hispanics. I think Governor Palin can help with appealing to women; and, I think both McCain and she can appeal to Hispanics on the issue of patriotism unless Obama tabs Richardson as his running mate.