I just fired a shot across the bow...its obvious you've done some real thinking on this...Thank you...
Couple of names I forgot about, just to be more through:
Tom Ridge - I think this guy is to wooden, and lacks carisma...however being close to Bush and ambitious means he's got to be on the list. I think he barely gets off the starting line but you never know.
Tommy Franks - could be THE wild card. Seems to have some Eisenhower-esque properties, and Generals are about the only ones who can get away with starting at the top.
I need one more for an even 20.....
Also, 2008 is too early but keep an eye on Bobby Jindal.