Indeed. That is the opposite. There are ways to give metropolitan areas more powers without making them separate départements, provinces, or whatever. The idea of a Montréal not part of Québec is a reactionary angryphone vision that always involves more bilingual signage and other attempts to erase French-language identity. There has been a movement across many countries to give cities more powers.
I don't see how the island as a whole getting such powers would be more valid than the city of Montréal, Laval and Longueuil - the west island is certainly as suburban and carcentric as the worst of Laval. Homelessness and semi-itinerance have spread far beyond the city centre and I'm sure there are cases in the largest and most urbanised of the suburbs.