Is there a Debian equivalent of Ubuntu’s PPA concept or plans towards that for bringing to Debian?
No, there is not yet such an environment. Work on this is basically stalled because noone has the time. I proposed such a project for last years Summer of Code (see http://wiki.debian.org/SummerOfCode2010/DeveloperPackageRepositories), but it was not taken up. The proposal also contains a rough outline what would be needed to implement it.