Just thought I'd start something!!
That is really unfortunate about the French teacher. I took French grades 6 - 12 and part of my first year of college. 6 - 8 grade, I had a very American French teacher with an absolutely beautiful (I realize now) French accent. Grades 9, 10, and 12, I had a teacher from Haiti, whose accent was so strong that we had a hard time telling when he was speaking French and when he was speaking English. 11th grade, a teacher from Quebec. In college, my TA was from Madagascar -- beautiful French accent.
After that little trip down memory lane, it is going to be really hard to approach the principal about changing the teacher without "sounding snooty" unless there is a concern about your child's rapport with the teacher or the teacher's professionalism toward your child.
It can be tricky when getting long term substitutes for things like maternity leave. You can certainly ask the principal about that without worrying about stepping on toes. It really depends on your area. In my hometown, for example, it was quite easy to find a sub who could do French class because we were surrounded, quite literally, by universities and colleges.