I haven't seen Peggy Noonan's column, but the prospect of Cheney resigning in mid-term to give a future Presidential prospect a boost (through VP incumbency) is not a new idea. It's been talked about quite a bit, with the most likely scenario being a health-related cover story for Cheney's resignation ("the VP's cardiologist advised etc.").

It certainly predates the hunting incident, which I predict will shortly become a non-issue in political terms -- yeah, he goofed, but it's a stretch to see a tie-in with competence issues on the job. In fact, Cheney's competence is not much in question; his agenda and ideology are certainly questionable, but his ability to push his agenda is pretty well established at this point (and he's not responsible for military planning; Rumsfeld is).

As to who would be the most likely VP prospect in this scenario -- my money's on Condoleeza Rice. In fact, while I wouldn't call it likely, it's not out of the question that we could have two women as the major party Presidential candidates in 2008: Condi vs. Hillary. It would certainly make for an interesting race (although it would probably result in another Republican win, since I think Hillary is so disliked by so many people that I would consider her unlikely to win in the general election).