Obviously, what Hillary & Co. would prefer is for the Michigan and Florida delegates to be grandfathered in. But she needn't expect any favors from Howard Dean, as relations between the Clintons and Dean have been frosty since 2004, for reasons John Fund laid out here.
Given all the caterwauling that the Democrats have engaged in over the years about fairness in voting -- starting in December 2000 -- this whole controversy is dripping with irony. How could Barack credibly challenge the "every vote should count" argument that the Clintons surely would trot out, if he were to attempt to argue against seating the delegates at all (which he probably won't, for prudential reasons)?
On the other hand, either grandfathering or the do-over smacks of unfairly "changing the rules in the middle of the game" (a fine Democrat tradition, manifested most recently in the Torricelli/Lautenberg rules rewrite in New Jersey). Barack has every reason to feel aggrieved that the do-over, if it happens, occurs later in the campaign when Clinton seems to be on the upswing. After all, he had plenty of momentum during the period when the original primaries (where he didn't participate or campaign, in accordance with the rules) were held, and he might well already have won the states had he broken the rules as Hillary did.
So in the end, either the Democrats end up not counting every vote (and waiting for the credentials struggle at the convention), or else they change the rules in the middle of the game. So much for the evil, vote-stealing Republicans being the ones who foul up elections, huh?
Finally, especially with a do-over, the whole point of refusing to seat Michigan and Florida in the first place will be nullified; instead of their states having no real impact on the process (the whole point of the DNC's original refusal to count their delegates), the "rulebreakers" in Michigan and Florida may end up having the most impact of all.