But seriously, why? There are very few french only airfields, and plenty where either there is a controller, so you can do it in english, or radio not compulsory and according to my local DGAC office this means if it doesn't say french only you can do it in english.
I think the opposite is true. Most airfields are indicated as French only, operated by an aeroclub. Of course people there will most likely speak English and while I am able to do radio communication in French -- without the ICAO endorsement, I'm not within the law.
My plan is to get an ICAO level 4 endorsement from DGAC. I was told carrying the certificate is enough, it doesn't have to be entered into your PPL. The German CAA at least does not enter French language qualification into any license because they would have to first officially recognize test centers.