No Death Tax for Family Farms and Businesses?

What if you stiffened the federal estate tax –say, a $1 million exemption and a 50% tax rate – but granted a generous special exemption – say, $5 million or $10 million – for a family business? To qualify for the exemption, family heirs would have to keep themselves on the payroll and not sell the business.

Could something along those lines, as envisioned by Ray D. Madoff of Boston College School of Law, actually work? Or would estate planners have a field day constructing "businesslike" tax shelters?