However, the 60 vote hurdle in the US Senate has a big hole in it at the point where a budget bill get scored as not requiring a waiver of PAYGO requirements. That is when the US legislative process defaults to the Two Chamber Majority system of its original design.

This is perhaps the most felicitous unintended consequence in decades.  Hoist on their own petard, indeed!  But that requires that Democrats have the will to seize that opportunity.  I fear that they are so in campaign contribution servitude to wealthy donors that they will be afraid to take advantage of this opportunity.  Perhaps if there is no other way forward and they can disguise what they are doing it might come to pass.  Clinton did get taxes raised on the rich in a party line vote before the '94 mid-term elections.

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."