In order to obtain a motorcycle license in France (permis A1 for example), must one necessarily possess a car driver's license? Is there any way to legally drive motorcycles in France without having already obtained a car driver's license?
Not at all. An A1 or A2 permit doesn't require to get a B permit first, or later. I've known people who got their A1 permit way before they B permit, and even one guy who never got his B permit, as he wasn't interested in driving cards.