Here are some thoughts for your consideration:
1. All 'non'marked' works get an automatic copyleft, not an automatic copyright.
2. Copyleft works can be registered for free, copyright works incurr a registration fee.
3. There is a yearly copyright tax imposed on copyright works, copyleft works are exempt.
4. The copyright tax is based on a percentage of the copyright holder declared value of the work.
5. The copyright holder will be encouraged to declare an honest value by having to sell the copyright to to work at the declared value or 5 percent above that value to any and all comers. At the value if the purchaser will put the work under a copyleft, 5 percent above if the purchaser will keep the work copyright.
6. Copyright status lasts for 10 years, then the works convert to copyleft for another ten then they go into the public domain.
7. Orignally copyleft works remain copyleft for the life of the author (and perhaps plys whatever.)
8. Works building on public domain works are not elegible for copyright status, only copyleft. (Does this make any practical sense??)
all the best,