Of course, the only reasonable and logical choice would be to field the mighty and infallible Chauchat! Those weak Germans would never stand a chance!French small arms anyone?
They were on forefront with the light machine gun idea and execution back in the Great war, and were also the only major country that developed and issued the self-loading rifles. They also fiddled a bit with the pre-intermediate cartridge with the 8mmx35, and with the pre-assault rifle for it.
In the interwar period, that level of innovation pretty much died out.
(see here the RSC models of 1917 and 1918 firing it out 100 years after the ww1)
So I'd suggest that they still have the RSC 1918 in some production, it will be using the left over 8mm Lebel cartridges anyway. Try and make the 7.5mm version of it in the meantime. A carbine made around perhaps the 7.5mmx35 round might've been usful.
The lack of a good, modern SMG also needs to be addressed. The light MG FM 1924 seems to be the only success story - so just make more of these?
Surprisingly enough, there was a lack of a modern repeating rifle in the interwar period - bar a the small number of MAS 36, it was the ww1 left overs and that's it? This also need to be rectified.
There is also no belt-fed MG for the Army.
Any worth in an ATR in 13.2mm calibre? It was not like the German tanks before 1941 were that well armored, after all.