Peter Pig, Essex and Battle Front can all contribute figures for the French Expeditionary Corps (FEC). The packs of heads from Peter Pig will be particularly useful.
For Vichy French just use 1940 French figures.
For French in US uniform use any US figures and do some head swaps so some Officers have Kepi and some men have Adrian Helmet. For additional variety you could mix in Peter SCW Republicans in Adrian Helmet or 1940 French figures, or you can reserve them for particular support units like artillery.
Use Peter Pig SCW Moroccans as Moroccan Tirailleurs.
Goumiers with their mix of native, British and US equipment pose the greatest challenge. Luckily Battle Front / Flames of War now have these guys.