If you take a step or two back and notice that what you are really trying to do is run a weekend team competition, does it really matter what eligibility rules you apply? In the limit you just need to find out who wants to play Saturday afternoons, what differences in standard of opposition they would accept and how far they're prepared to travel. From that you structure teams. County leagues are a convenient focal point if you have to build a weekend team out of a coalition of midweek league clubs.David Pardoe wrote: I believe the competition should be far more focused on players who actually live and actively play within the recognised localities/counties
Basing eligibility on ceremonial counties is one way of doing things and historically British amateur sports and games used that approach, probably taking the idea from cricket. Professional and top level amateur football and for that matter both codes of Rugby were very much more club based.