You'll have to wait for FCL.008's report and NPA for a definitive answer, but my impression is that the flight would be an IFR flight like any other
Bookworm
Seriously my flippant earlier post aside how do you think that will work?
As you suggest you file IFR in France. Presumably the Contoller may still give you a SID and presumably you may enter cloud on the SID at a lower altitude to which you are entitled. Does that mean that you ensure the cloudbase for the whole of the SID is above the minimium cloud base and if it isnt stay put on the gorund? Alternatively do you build in a degree of common sense and accept you may enter IMC at a lower altitude and if so how much common sense do you build in? What do you do if you are in an out of cloud on the SID because the cloud is broken with elements below your minimium IMC altitude? Do you base your go dont go decision on the base of the very lowest cloud anywhere in the area of the airport from which you are departing?
I fully accept that on most occasiosn the cloud will either simply be too low or too high to be of concern. However is there a danger with limits such as these that the rules simply get bent when it suites in which case why have the rules in the first place. Moreover on marginal days does it encourage pilots to go because they know / think the base will lift en route and therefore they set off VFR with the intention of staying below the base in the hope of a pop up clearance en route.