That's one of the most intriguing solutions for sorting out copyright law I think I've ever heard.
Ordinary copyright holders automatically keep rights for the valuable life of most works; if they still want to withold it from society for a period after that, they have to pay. Large evil corporations can keep the rest of the world from benefitting from its old works as long as they want, but has to pay back the commons for the privilege.
What's more, if you calibrate the extension fees to be competetive with the cost of lobbying Congress every time the copyright period threatens to move past the creation of Mickey, you might present Disney et al with an economic incentive to support the change...?
I'm not enough of a public policy geek to see how all the details would sort out, but that is one interesting idea. If I had mod points, you'd get 'em.
Anyone can make an omelet with eggs. The trick is to make one with none.