Awesome idea.
But how would you categorize everything? Without a publishers consent you can't declair compatability. So how are you going to diffentiate in a meaningful way the difference between Spycraft 1.0, Spycraft 2.0, Grim Tales, Conan, True20, etc?
I mean if Mearls is posting his own stuff up there, he can put it's title on there if he pleases (and owns the rights to it!). I'm pretty sure d20 Modern & D&D d20 can be listed by name as well as BESM d20 & d20 Mecha (which are both in SRD Form).