DD- If you're suggesting a commercially produced round, I would think that the .22 CCM would be the best starting point. Shorten the COL to fit through long rifle length actions and keep the pressures in the .22 RF levels and you could re-chamber existing RF rifles and modify / replace bolts for a center fire pin.
One problem that I encountered when I was developing RF equivalent loads for the .22 Hornet was the lack of availability of commercially cast .224 bullets. I can't see re-loadable .22 LR equivalent being a success without commercially available cheap bullets.
