I'm no wonk, but it seems to me that something along these lines would work:
1. Set up a robust public option plan.
2. Establish a state-by-state trigger that will dump states into the public option if they qualify under certain circumstances, but make sure that in reality most states will qualify immediately.
3. If states do not meet the trigger, allow them to opt-in to the public option if they so choose.
4. If states do meet the trigger, allow them to opt-out of the public option if they so choose.
5. Any state that qualifies for but opts out of the public option must set up a Conrad Co-Op. Except for North Dakota, which can have one in perpetuity, for all anyone cares.
(Unfortunately, if that doesn't get 60 votes, step six involves bombing Iran. But it's a start).
Realistically, I think what we're headed for is a weak public option with an opt-out; actually, I don't think that's going to be the sticking point in the end. What's a little harder to see coming together are the affordability and financing compromises.
Liberals, in my view, should be concerned with two things above all at this point: first, the short-term effect of reform on large voting populations, and second, adaptability of the bill to future changes. Get something that can be built on and that won't cost Democrats any elections in 2010 and 2012, and everything else can be negotiated.