Yes, but unfortunately Polish Army on Eastern Front had different uniforms than Red Army and it would need new playermodels
The only difference was the jacket and of course Rogatywka cap, rest of the uniform and equipment was the same like standard russian ones. Also, Rogatywka wasn't very common on the battlefield as most of the soldiers wore russian helmets just with wz. 43 "polish" eagle painted in front to stand out. Btw, if somebody would ever like to create polish jackets they are almost identical with german ones with different marking on the collars (obviously) and lower pockets being moved to the sides instead of being in front like the upper ones on the chest. Maybe it is possible to create them by modifying german and russian uniforms? Have no idea about that, but having Rogatywka and a proper jacket opens the way for the early war polish campaign in FH2
At first they received Soviet uniforms but in summer 1943 they get their own model which was based on Polish wz. 1936 and Rogatywka field caps.
True, but change wasn't that fast due to shortages in russian supplies. The first to recieve new uniforms were officers (who btw, very often were polish speaking russians) so by the time of Battle of Lenino somebody mentioned here, which btw, was first battle for the Polish 1st Kościuszko's Army, many privates still wore russian uniforms.
When it comes to western front then yeah, Polish would wear british uniforms with polish markings and that's it.