This is a very important consideration. Now, I think the assumption behind the question is that aboriginal persons do not speak French. This is an assumption that is not borne out in many cases. I would say, without going to much into detail, that several of the names of first nations individuals or aboriginal individuals who were mentioned as potential candidates for the Supreme Court are indeed bilingual.
I have great sympathy for the idea that one day there should be an aboriginal judge on the Supreme Court of Canada. I don't think the requirement of bilingualism precludes such an appointment.