Interesting post! I agree with much of your analysis but disagree with your main conclusion that:

Far from being undesirable, we actually need more “fiscal cliff” like deadlines in the future – because in Washington today that’s the only way the parties are going to get serious, put their cards on the table, get a partial solution, and (gasp!) realize that in the end, the compromise was mutually beneficial.

I think creating more scenarios like the fiscal cliff to force "compromise or else…" is a recipe for disaster: some time is bound to arrive where no compromise will be reached despite the elaborate set-up to force one lest disaster follows... and disaster will follow.

Instead, I think that the parties should abandon the concern with long-term policies (like the size of the government, the deficit and entitlement programs, two decades from now) that require Grand Bargains, and address only short and medium-term problems where compromise might be easier, because they cannot foresee what unexpected problems and societal changes there will be over such long times, and their current decisions cannot bind the future government anyway. In addition, the US should try incremental moves (like eliminating or reducing the filibuster) that make it easier for an elected party to enact its agenda without so much veto power to the opposition, thus eliminating the need for Grand Bargains. Let the voters throw out the rulers if their policies are too extremely partisan.