This thread is quite old but I thought I'd post this info for anyone looking for answers.
The French government / consulate have reassessed their process for domestic helper working visas. It's still quite involved (they are french after all) but instead of the negative response we were expecting - our helper's working visa came through a week after we sent off the request.
Here's the link to the page that has all the relevant info.
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The most difficult part of the process was trying to find the correct "department" in france to email the scanned form (you need to apply to the area you will be staying in the longest)
Definitely worth a try for those who want a "holiday" :)