So Napoleon II is born about a year before the disastrous invasion of Russia starts. The British have a strong position in Portugal. Austria had recently been pacified during the war of the fifth coalition. And tensions with Russia are rising. I imagine Napoleon's marshals would want to set up a regency but would that regency be moderate enough to repair relations with France's neighbours? If so, what would it take for Britain accept a long term peace? Would another coalition form to return lost possessions to Prussia and Austria? Would Paris still support a Bonaparte king in Spain.