While I'd love to see copyright terms just tuned down across the board, I could deal with a system whereby the next extensions required explicit renewals. For practicality's sake I might even be willing to put up with allowing owners to file one form for their entire catalog rather than enumerating everything, because if nothing else at least this would clear the zombie owner backlog.
I agree with this and I think you could even scale the fee for renewal up over time to discourage just automatic renewal of stuff that has almost no commercial value anymore. Seriously I could care less if disney wants to keep paying for steamboat willie to stay copyrighted as long as the fee keeps going up making them think about the value of doing so.
Initial copyright, until 1976, was for 28 years, registration required, with one renewal allowed for a total of 56 years (if I recall correctly).
While registration is still possible in the US (and is required for certain damages), it's not required. I agree that this would help greatly in addressing the matter of "orphan works".