2000kg would be a good start, although I see no reason to exclude light twins from this. Up to 3 or 4 tons would be perfectly acceptable and stuff in that range will be heavily restricted by insurance requirements and affordability anyway. Limit to 4 POB fair enough, but not a seat limit, that just makes pilots squeeze as much as they can into a 4 seater instead of using a 6 or 8 well within its limits, increasing the dangers. Touring the country with the wife and kids in a Baron or Seneca day VFR, would be way safer on a lot of levels than trying to squeeze everything into an Archer or Cirrus. Most of these rules clearly show they are written by those with little understanding of aviation and it's actual risks.