I'd consider Subversion to be better than both Git and Mercurial if those changes were made (and implemented well). Subversion has a long history and plenty of tools already interacting with it that make it worth saving.
The whole point of SVN was to bring CVS up-to-date. People use it because, for whatever reason, they want a modern CVS. I'm not sure you can improve it without sacrificing the familiarity that's really SVN's primary asset.