I may be a bit biased here as it's something I helped create, but have you looked into Gantry::Conf? It does some of what you're after, and might be a good starting point. It doesn't "convert" the files, but it does create an abstraction so the application doesn't need to care "how" the admin/implementor/etc choose to config it.

Also, just an FYI, but Gantry::Conf doesn't rely on any of Gantry itself, so it could easily be moved into its own distribution if this type of idea catches on with the community.