I'd approach this from a different direction. I think the purpose of copyright should be to remunerate creators, not to control their works - controlling the works just happens to be a good way for the creators to get paid. Thus if you're unable to legitimately acquire a work (distribution stopped, or geographically limited), it goes public domain.

I don't disagree, but I don't think this would not work for all copyright. It might work for "personal use" reproduction - books, video games.

I don't think it would work for the 'public performance' part of copyright - composers, playwrights, movie directors.

For example, a lot of contemporary music is not published at all. If you get a score from the composer, you still have to pay royalties when you perform the music publicly.

If I am not mistaken, this used to be the case in Germany before EU copyright "harmonization" - if something was not commercially available for two years, then it was legal to make copies for personal noncommercial use.