As Krugman points out, the situation in the US is a pretty sad sight, with the lamest of lame duck presidents fiddling while the economy burns. This is a pretty ridiculous situation. Why not do what they do with buildings and start using them before they are officially opened?
What would be wrong with the incoming president having executive power from the time it is clear they are the president elect but, if the (somewhat strange to our eyes) tradition of not naming one’s cabinet until after the election is to be retained, the president elect could operate by directing existing executive officers as well as replacing them if he wished (with temporary or permanent appointments). Sitting around till well into January while the place goes to the dogs seems barmy.
Perhaps at the end of his term Obama might offer such an arrangement to his replacement. It can’t be much fun sitting around waiting for the new guy to take over in any event.