As a suggestion, the Metal Archives seems to just be all about music. What if you would be able to expand the Archives by having the ability to add more things about Metal: as in Books, Radio Stations, DJs, Movies, etc... all based in Metal.

That would be incredibly hard to fill out...

Huh, no.

Consider that with radio stations and DJs, there is little objective information about them to archive, nothing really comparable to an album or a demo from a band, just a playlist, a compilation of existing information. Information about them will often be obsolete in a year or two. Perhaps a forum thread on those could gather info, but they're also highly localized most of the time.