I think that this is a very interesting possibility. Let me point out two initiatives, one at the post-secondary level and the other at the secondary level. At the post-secondary level, as you mentioned the University of Ottawa directly encourages students who have followed immersion courses in high school to follow French courses at the university. There is a mentoring program to allay the fears of some students who might feel that they won't be able to follow the subject matter. The mentoring program is a way to help the students.
Regarding the secondary and primary levels, I would like to point out the role played by the Edmonton Public Schools school board. It is really ahead of the other school boards in Canada. It offers quality programs. One of the results of this program is that the vast majority of the students studying at the Saint-Jean Campus, the francophone campus of the University of Alberta, have followed an immersion program that enabled them to acquire the skills for doing their post-secondary studies in French, as well as the confidence that they will succeed.