Considering his time as Eisenhower's vice-president, it would be reasonable to expect him to be a good one; but...I wonder if that was the real Nixon, of just a reflection of Eisenhower; and for that matter if there was a real Nixon at all, or just a protean blob of politician- goo.
If there is a single more appropriate human illustration of the downside of the idea that you can be whatever you want to be, then I submit that it is as yet unknown to political science. Nixon turned himself into how many different men over the course of his career?
Not that he was easily led- pretty much the opposite, it was his temper that brought him down- but that he made himself over into whatever he thought would bring him advantage, again and again, and he was just on the edge of the generation that could do that and have it go no more than skin deep; with Nixon, it was a sincere pretence, if you can parse that at all. Political method acting.
As such, it's hard to tell what he would have been, except what he thought the people thought that a president ought to be- and how well a man whose character was formed in the Depression would have read the Sixties, I have my doubts. I think he'd have tried to play the wrong part- been a Teddy Roosevelt in the age of Kennedy.
How this would have played on the international stage- he would have tried to pursue America's interests coldly and rationally, but his methods would not have been purely rational- he would have acted a part; and how coolly reasoning his perspective would have been, I could see it all- especially with the middle east in the early seventies- all going horribly, horribly wrong.