Should have checked before saying something.. you're absolutely right, indeed FFVP mandated the Flarm but FFVP does not operate the airspace so I would guess that in theory you could fly without it there, which would be consistent with the multiple foreign pilots who go there without it.

I guess basically you wouldn't be able to take-off from an airfield operated by a FFVP affiliated club but you could fly there without this device. Like some power airplanes transiting in the area.