Improvements on CPAN are always welcome. You just have to remember its basic principle: make life easy for authors. In other words, the barrier to entry should be as low as it can be.

So the basis of CPAN, the mirrored repository of plain tarballs, IMHO needs to stay the same. Some authors don't like RT, or web forums and don't even use source control. That's fine. Their contributions are no less important than those of "good citizens".

That said, there is certainly room for improvement, and in fact in the last few years, a lot of work has been done _above_ the current CPAN: RT, CPAN Forum (is it missing features?), Anno CPAN,, CPAN Testers, CPANTS... and recently alias's Top 100(s), amongst others.

Now it's true that all those sites do not have a common look and feel, but it looks like people are taking notice and doing something about it.

What's missing there from your list are mostly GitHub specific features, but nothing prevents you, or any other CPAN author, to use it. It looks like they do actually, as a search on Perl shows 1592 repositories. And if you don't like GitHub (I don't), you can use an other repository (launchpad seems nice enough).

What I want to say here, is that instead of planning of completely redoing the CPAN, maybe working incrementally on what you don't like (improve CPAN Forums maybe?) might be a more practical solution. You won't be alone in doing this.