Really? So you're arguing that defrauding Medicare is fine?
First, it's clearly wrong and amounts to theft of assets from taxpayers.
When you get into the legalities, there are some applicable cases. For example, a court has ruled that sham divorces when used to allow employees to receive accelerated pension payouts were not legal and the pension plan could recover the money. It actually says that the divorce can not be reversed under ERISA, but suggests strongly that if Continental had filed under state courts, they could have won.:
Court Decision Denigrates Marriage - Or Does it? (What's Wrong with the World)
Or, more to the point:
Family Law Prof Blog: Sham Divorces
Read what it says - sham divorces can be vacated and the financial outcomes reversed. There are a number of cases where sham divorces have been reversed.
Now, if it's a legitimate divorce, it is perfectly legal, of course. But since OP indicates that the entire reason for the divorce is to protect assets, that almost certainly counts as a sham divorce - especially if the couple continues to live together.
So please stop advising someone to do something that's illegal and wrong.