I think you've got some good ideas here. I'd suggest making the first registration free, however (even for the span of 20 years that you suggest). I'm not so worried about the Copyright Office or whomever having to maintain a database of who published what when, because Google and the Internet Archive pretty much have that covered already.
After 20 years, the original author has gotten fame, glory, and whatever small amount of money they can out of the work, and then a fee to maintain the copyright seems reasonable to me.
