Okay, this is possibly a complicated idea. Essentially, I prefer to play most games without any filtering options - Low-res textures, when filtered, start to look blurry and this makes my eyes protest. I've been playing Hexen II with GL_Linear however, because the blocky shadows manage to bother me more than a bit of filtering does.
The request is to have a "smooth static shadows" option, so that map shadows are effectively filtered while textures remain unfiltered. I suspect this is possible, as I have noted that hitting shadowed areas with Lightbringer will display a smooth lit-up circle, even in GL_Nearest mode. Judging by the way static shadows are layered onto textures, I hope that this would be a possibility.