Well I decided to follow Alessio's steps, since I believe theme localization should be a global project.
I have setup a "slash-french theme" project with a structure similar to "slash-italian theme".
It's empty right now. Don't expect much news until 2 weeks. Unless some decently speaking french guy wants to volonteer and speed up the process...
BTW, Slash 2.2.0 is my target version.