"The party has stamped Kerry's candidacy more than Kerry has put his imprint on the party..."
This could be a flaw, but not if he turns it to his advantage. I've written about a similar idea before when I still was hoping Dean could turn it around. This election is bigger than Kerry, there's no way around that. So what Kerry should do is market a platform, a label, a system, that all the Democratic candidates can get behind.
If we had a Democratic version of Contract For America, that would actually be marketed as a document, or a badge, or something tangible, then it could be a nationwide movement that would actually lend momentum to a whole crowd of Democrats, with Kerry as their leader. And it's very much something that could be used to triangulate the Republicans. You make it about being honest with Americans, but you present it in a partisan fashion - put the Republicans in the position of having to run against honesty. You make it about civic education and open information, and put the Republicans in the position of having to defend secrecy and obfuscation. You don't need to make it about Democratic things that can legitimately be opposed, like multilateralism, or minority rights. Everyone knows the Democrats are about that.
You come up with a smartly marketed theme, a tangible something that people can brand themselves with - I keep thinking of a document - and we've graduated from a bunch of individual races to a movement.