I don't agree with this prohibition, and I doubt that it's likely going to achieve much, but if my experience looking at past government restrictions on things that people want to do is predictive of the situation here, it'll mean that someone will sit down and figure out the exact limit that the French government prohibits and then figure out a garment or combination of garments that accomplishes as much of the original aims as possible without crossing whatever specific garment line is there.

I mean, what's a women's garment that does the head and neck? The bonnet?

googles

Hmm. Apparently it actually did have some religious background.

https://en.wikipedia.org/wiki/Bonnet_(headgear)

Bonnets remained one of the most common types of headgear worn by women throughout most of the 19th century. Especially for a widow, a bonnet was de rigueur. Silk bonnets, elaborately pleated and ruched, were worn outdoors, or in public places like shops, galleries, churches, and during visits to acquaintances. Women would cover their heads with caps simply to keep their hair from getting dirty and perhaps out of female modesty, again, in European society, based upon the historical teaching of the Christian Bible. In addition, women in wedlock would wear caps and bonnets during the day, to further demonstrate their status as married women.

But, as far as I know, they aren't banned. So someone says "Okay, so people can't wear (religious) abayas, but can wear (secular) trenchcoats? This new garment isn't an abaya. This is a bonnet and trenchcoat." Or, you know, whatever.