I was going to ask about possible VPs... So, Nixon as President from 1955-60, and possibly to '64. But is this really the relatively pragmatic, "only Nixon could go to China," version we know from OTL?
I would presume that 15 years earlier than OTL, he has differing views to those he would later hold. Some of this has already been covered - might he in fact come down one way or the other with the Red Scare, either encouraging it or ridiculing McCarthyite excesses?
Nixon got in and gained power under the "red scare", which is why conservatives could put up with him, but in a general sense he was always quite the pragmatic man.
Without the defeats of 1960 & 1962 that should be a plus that hopefully outweighs the plus of his OTL successful law career.
I've always thought the Kennedys motivated by Joseph's driving ambitions. Plus, by 1964 it's possible that JFK's Addison's has advanced to such a stage that running for office isn't feasible. You might be right, however, that 1964 is a bit earlier for RFK to run, particularly with the like of Humphrey and LBJ.
I do think that it was JFK's death that propelled RFK. If you look at RFK in an even light most days he's not a great campaigner, not terribly likeable in public, and his best speeches are motivated by urgency and tragedy—I can't imagine him stumping during a normal campaign (see, for example, his fairly average '64 Senate race which was won because of money and staff, not his ability).
You're right that the VPcy in 1960 was viewed in a far different light in 1960 than it is now, but I think it all depends on how MacArthur works out as VP. There's a chance, however, for Rockefeller to accept: Nixon will be looking to cultivate an orderly succession for Republican policies, I think. He thought of the VPcy as such a role; I suppose then the question is whether Rockefeller decides to accept, given the differences between Nixon and Rockefeller. I'd expect those differences are fairly small or at least overcome-able.
Nixon might, as he did in '68, find the person whose blandness effects the ticket not a whit and that would leave Rockefeller with the second highest Republican profile around.
I think it boils down to a couple competing factors. The conservative activist faction, than in its infancy, will object to Rockefeller. Goldwater, as he did over the civil rights Nixon-Rockefeller deal of OTL 1960, will object. The progressive faction wants Rockefeller. The Main Street faction is probably happy with Nixon, and doesn't care. Southerners don't matter yet.
I could see Rockefeller having the stature that Nixon is forced to offer him the VP slot, but Rockefeller agrees to stay off in return for? Likewise I could see Rockefeller accepting, in return for a new civil rights or city compromise.
Frankly, Nixon has enough clout (depending if he wants to use it) for all sorts of VP scenarios.