It is a bad idea. It wouldn't work. It's far too niche, doesn't quite fit 2012, and wouldn't generate anything on the terrestrial side, this is why XM and Internet radio exist. It's almost amusing Philly is lucky to have one of (if not the) most successful Alt rock station in the post 2000 era and people still find a way to rag on it. Nearly all of the supposed 'hard' alt acts you originally mentioned get played a lot(and most of THOSE aren't even hard and Korn isn't really alternative anyway)
Tell me about it. New Yorkers don't have an alt rock station of ANY kind. And I do tend to hear Tool a lot on 104.5 when I listen online. I would say that while RFF plays more softer artists from the 90's (ie, Goo Goo Dolls), the alt rocker we used to have, RXP was softer overall with an AAA lean (with classic hard rock like AC/DC thrown in once in a while).
I live in Jersey, where the only choice for any current rock we now have is WDHA, a sister station of WMMR. I've compared their playlists and I can tell you that DHA relies A LOT more on classic rock. I think I remember someone told me that Greater Media also owns a classic rocker in Philly but not in Jersey, which probably explains this difference.