Hi terminator,
There is a site
www.niehorster.org that gives an idea of what units and what size each nation had in 1941.
My understanding of "mountain infantry" is infantry specialized in mountain warfare where you have rocks all over the place so it is not easy to dig in.
Developing a list of units is a mission for lifetime. Look at Panzer General II, a game with years of history and many mods. After 20 years of modding they still make improvements. The original German "Jager" unit - mountain rifles - is very different from the mountain rifles you see in latest mods. If I could make new units I would have "mountain infantry" of 1941 as regular infantry plus extra MG/mortars/whatever they need and the only time Germany or USSR has real mountain infantry in 1941-1942 is Caucasus.
By the way, I am still working on my 1941 campaign. Maybe in the next version my mountain rifles will be different?
Cavalry entrenchment - my first guess (that may be wrong) is that cavalry was mostly used for attacks and even if they were "infantry on horsebacks" maybe they would not be as good as line infantry in holding the line. As long as the stats are the same for all nations.
The art of war is simple and esay to understand but fighting a war is hard.