Assuming France can take over the heavy lifting, will they?
No, they can't, and they won't either. If France were to do the heavy lifting outside the EU umbrella Greece would suddenly become France's problem, and not EU's problem. It would also become politically unsustainable for Greece, because Greece would become almost a vassal state of France. After a couple of quarters we would see Varoufakis complaining about the French imperialistic attitude and Schauble telling the french "told you so".
I think they should go to a non-cash full electronic currency when they drop out of Euro. That will help with tax collection and tracking fraud, also the logistics may be simpler than introducing a new paper currency.
For this Greece would need a kind of IT infrastructure that simply is not there, and also there would be issues regarding payment systems and legal issues. It wouldn't be an easy feat. They will be better actually planning for a Grexit with a paper currency instead of trying something that fancy.