As far as becoming a librarian goes - with a BA and a subject Masters, you are well on your way to being qualified for a position in an academic library. Public librarians are not typically required to have a second (subject) Masters, but it could be useful in some special collections. The last credential you would need would typically be a degree in Library Science (Masters level is usually the terminal degree for work in the field, though some do pursue a doctorate if they get involved in research). The University of Western Ontario in London and McGill University in Monreal both offer Master of Library and Information Science programs.
As far as becoming a radical librarian - I will leave it to others on the site to contribute their thoughts. In a way, the answer to that question is what some of those involved in Radical Reference are trying to figure out.