If Romney does not pick someone like Marco Rubio or Paul Ryan, I will be very disappointed. I have a feeling he will be picking a conservative rockstar economist, and I hope that feeling is correct.
Economics isn't where he's weak, and picking Rubio would have nothing to do with economics and everything to do with the Hispanic vote.
As much as Condi and Romney both have done to defuze this rumor, I'm surprised it keeps coming up, but I think there are several large holes in your thinking on it.
Romney doesn't suffer from Terminal Charisma Disorder like McCain did, so a VP pick is not as crucial to fire up the base for him as Palin was for McCain (Who would have lost by ten MORE points if not for her). His VP pick is therefore not nearly as important for making up the charisma gap as McCain's was, but it IS very important for broadening the base of the party beyond the 'Old White Male Anglo-Saxon' meme the Democrats are pushing on the GOP, which would make Rubio a good pick but Ryan wouldn't bring him anything he doesn't already have covered. A candidate with some sort of positive foreign policy experience and who is also either Hispanic or female would be the ideal choice to address Romney's
curriculum vitae shortcomings, but pickings are fairly slim on checking both of those blocks, so he will very possibly have to decide which of the two matters more.
Obama's reasons for having Biden were essentially because (Laughable as it seems to a non-Democrat) he had many years of foreign policy experience due to his Senate position, although a rational person would say it was many years of screwing up our foreign policy. Nevertheless, it filled a hole in Obama's resume that no amount of lying or MSM hand-jobs was going to cover. And, of course, because Biden was not a Clintonista.
Dr. Rice would bring two things to Romney, the most important being real (And competent) foreign policy experience. Less importantly, she is on record as pro-Second Amendment and right to self-defense. Her position on 'Right-to-life' vs. 'Choice' is unpalatable to a lot of the base, but given where Romney has been on it himself, hardly a showstopper; her position is more in line with the social values of people who aren't counted in either party's base, so it probably nets out to a wash if not a minor plus with gaining more swing voters than it costs in one-issue base voters, plus it would provide great amusement to see NOW and other feminazi activists tie themselves in knots and blow their fuses.
But, she has been quite clear that it ain't happening.