The idea is specifically to solve the orphan works problem.
Practically speaking, life+70 is not that far off from perpetual copyright anyway. Nobody cares if a book published today will be escheated to the public domain in 2093, and very few works from 1927 are valuable enough to retain copyright today. In fact, it's so valueless that the vast majority of works still under copyright do not have public documentation of title. The only way to find out who owns these works is to get sued for pirating them.
So the idea is to create some kind of small formality that people have to jump through in order to retain ownership over a work, because vastly more works will hit the public domain even if it means Mickey Mouse will always and forever live in a cramped pet store cage shaped like a circle-C.
How to define "commercially viable" is... complicated. You can either make copyright fully pay-to-play to soak Disney, or you can err on the side of cheap renewals. I've also heard talk of sliding-scales based on taxable value of the property under copyright. I don't think it really matters as long as we have a reasonable process to strip orphan works of their copyright protection.
Mickey Mouse should be under copyright and Mickey Mouse should be taxed to an inch of his nasty rodent life are two separate questions and should be handled as such. A small fee should be fine (much less than the total cost of a patent, say) perhaps with a requirement to keep the work publicly available (print on demand and digital makes this relatively easy).
Practically speaking, life+70 is not that far off from perpetual copyright anyway. Nobody cares if a book published today will be escheated to the public domain in 2093, and very few works from 1927 are valuable enough to retain copyright today. In fact, it's so valueless that the vast majority of works still under copyright do not have public documentation of title. The only way to find out who owns these works is to get sued for pirating them.
So the idea is to create some kind of small formality that people have to jump through in order to retain ownership over a work, because vastly more works will hit the public domain even if it means Mickey Mouse will always and forever live in a cramped pet store cage shaped like a circle-C.
How to define "commercially viable" is... complicated. You can either make copyright fully pay-to-play to soak Disney, or you can err on the side of cheap renewals. I've also heard talk of sliding-scales based on taxable value of the property under copyright. I don't think it really matters as long as we have a reasonable process to strip orphan works of their copyright protection.