350lbs or 159Kg is a sensible min weight. Much like the B-class used to be.
I have suggested earlier that a new 20 foot formula class should be based on the old B-class design envelope with some additions. E.g. upwind sailarea 25square meters and 45-50 downwind, double trapze and the an affordable min weight attainable for home builders. The rest like daggerboards, mast controls, mast crossection etc. to be determined by the builders. No foiling, except alternatively for T/L foils which dont exceed the platform max width.

To make sure the boats are versatile, I would definately require them to be rightable by crew in all conditions. Further, all championships should include a distance race.

But we have discussed this a lot earlier. What we need is the magical mix of interested sailors with the will to get some boats in the water.