I would stay away from any sort of pilot sign up sheet, as most every event that we've done that has had moderate results at best.
I guess you could couple the idea of fully staffing Boston (like REALLY stuffing it with controllers, not just the usual) with the FFTF event. Perhaps you could do this for the first 3 or 4 hours only, as a kick-off to the event. I guess you could try and fully staff Boston both nights, but I think you would have significantly less traffic the second night, and the idea might 'lost its magic.'
But honestly, I would like to see a 'Staff Boston to the fullest extent possible' sort of event every few months, not necessarily coupled with some major event. Again, it would be very low key. Just simply have controllers sign up for positions, and then say 'Hey pilots, on this day we're going to staff Boston, so fly wherever you want, whenever you want.'