Let's change Fred's, $($from question $4),$ circumstances. His wife, Christina, is not a US Citizen. He comes to you before he dies and says that he wants to make sure that Christina can receive his assets $($which will exceed $$16,000,000)$ when he dies and have the unlimited marital deduction or at least defer estate taxes until Christina dies.

Is there an estate planning tool $($trust or otherwise$)$ that can allow Fred to transfer his assets at death to Christina and be able to use the unlimited marital deduction? If yes, what is it$?$