...If Bay State legislators will refuse to pass the law demanded by the court, and Romney will refuse to sign such a law and orders the bureaucracy to ignore the court, what could the court do?
Courts have fashioned their own remedies in the past, getting involved in minute detail, if they felt they had to. This Court will just simply declare that being gender opposites is no longer a qualification for marriage, and will order lower courts to accept applications on that basis. All subordinate courts are bound by the state's Supreme Court, and they won't even bother ruling against a gay couple who brought a case based on a refusal of whoever registers marriages to do so with theirs.
The Massachusetts Supreme Court did not set up the 180 days as a period of time to allow people to thwart it. It could have ordered gay marriages to be registered immediately. It was giving the governor and the legislature a chance to avoid a Constitutional battle on the US level, and adopt a civil unions plan.
If the governor tries to stick a finger in the Court's eye, he might find their fist back in his face. The time for setting off the BS alarm was years before, when these cases were making it through the lower courts. It wasn't possible to get an anti-gay-marriage amendment through the MA legislature then, it won't be possible now.