In fact, Dr. Hotze here in Texas has one such lawsuit making it's way through the courts as we type. Dr. Hotze is challenging Obozocare with a two pronged approach.
First, as mentioned, violation of the origination clause which in essence states that any law that levies a tax MUST originate in the house of representatives. The affordable care act did not.
The other deals with a portion of the 5th amendment because the affordable care act compels employers to pay private health insurance companies for health insurance.
I listened to an interview with Dr. Hotze and his lawyer and was very encouraged. Although it has taken many months for this to go full circle...John Roberts may be smarter than we give him credit for. The supreme court has not ruled on the origination nor 5th amendment previously...leaving Obozocare wide open and vulnerable to be stuck down lock stock and barrel... not simply modified.
Take a look at the links:
http://www.prweb.com/releases/2013/5/prweb10715298.htm
http://drhotze.com/2013/09/supreme-court-to-consider-new-obamacare-case/
Why force another challenge to the law? Why not simply rule it unconstitutional? What advantage is there to what you say is Roberts' MO?