Sanders announces Fmr. Governor Brian Schweitzer, originally considered top pick for Secretary of the Interior, will be the head of the Office of Management and Budget, pointing to large ending fund balances in Montana, and his commitment to Universal Healthcare, which was a large part of Sanders' platform. Schweitzer has stated in previous interviews that he believes a healthcare system based on Canada's system would actually save the United States money.
This leaves only the positions of Secretary of Transportation, Secretary of HUD, and Trade Representative left, although Sanders may have to find a backup for Secretary of Education.
You should pick Caroline Kennedy for Trade, Jeff Merkley for HUD, and Martin O' Malley for Transportation, Also you should make Chelsea Clinton Ambassador to Japan