I've been spending a little time on the new literature site, and they get a sh*t-ton more questions than we do. We would benefit greatly if we could attract more lit people, as the lit people we currently have tend to be excellent contributors. There are many sci-fi/fantasy fans on lit that read the genre authors heavily influenced by "the classics".
It's true that Blake's mythology tends to be a subject traditionally covered by English Literature, and while that us useful, I'm interested in the analysis of mythographers, which I consider to be the most fundamental.
We do allow Milton, so possibly this is a moot point and Blake is already within our scope.