If your scenario plays out, Obama had better hope that they strike the whole law and not just the mandate.
If they strike the mandate but not the regs, Obama will have essentially double-crossed the health insurance industry. The deal they were offered was 50 million new paying customers at gunpoint, in exchange for the pain of Sebelius and her regulations. The lack of severability was done to protect them in case the mandate were to be tossed.
For Obama, crossing the insurance industry is the political equivalent of crossing the Mafia. Remember Harry and Louise? They are going to use their massive warchests, plus Citizens United, to absolutely bury him under a blizzard of negative ads this fall.
He’s given them little choice, to wit “don’t legislate from the bench” which they’d have to for repairing any excised components, and “don’t overturn anything passed by Congress”, leaving them no option but to rubber-stamp approval of an existing law which is incompatible with the Constitution. This, plus your points about double-crossing the industry, brings every potential outcome to simple & complete overturning of the entire law as the only viable path. Notwithstanding the judges having already decided, any justice still persuadable would have to side with vacating the law in question insofar as this is the only way to satisfy such extraordinary demands by POTUS.