I think much of his "Domestical" life will reflect in the the things he'll try to do as regards US "Domestical" policy. You can do quite a bit with the stroke of a pen. Reagan, for instance, instituted a "We ask, Don't join" policy as regards to homosexualizing the military and he ended sex-integrated basic training in the army; both by executive order. No doubt, Rudy disagreed with both.
You must put National Security first and Rudy will do that.
So will McCain I believe but he is so hated here he is unlikely to get the nomination. Most of those opposed to Guiliani do not loathe him with the same degree of loathing nor do they think he is nuts as they do McCain.
I don't know about Romney but find him less likely to get the nomination.
Any of the others who would be fine in the National Security area are simply extremely unlikely to get the nomination. Most are running for the VP spot in any case and would be excellent in that spot building a national following for the next contest for the Presidency.