This is, I think, a more problematic prospect than most people realize. Far too large a proportion of the party's rank-and-file are anti-war for a nominee to position herself as a credible Iraq hawk. Conversely, far too large a proportion of the party's national security elites were pro-war to put together a viable anti-war team. The truth of the matter is that most pro-war liberals seem willing to privately admit that they were mistaken about the war (I was), but don't want to publicly say so lest their credibility take the hit that necessarily comes with admitting you were wrong about a very important issue. The best way out of this dilemma would be for Democrats to focus on the issue at hand -- what do we do now -- but that gets you back to the basic point that given the mistakes of the past, nothing we do now is going to produce a particularly happy outcome.
At some point the "hawks" are going to have to admit they fucked up. The only credibility they'll lose is with the kool kids klub, but they need to stop caring what they think anyway.