One thing that really bothers me about the cossaks as listed, is that it looks like an elite cavalry unit. Now my views on the unit is coloured by the relative high numbers of the unit, compared to other public unique units, and that "cavalry" has the top mounted unit in Civ 2.
Cossaks were light cavalry units, like hussars or uhlans. While there were Guard Cossak units at least during the napoleon wars, the cossaks were used mainly as raiding forces (and later like in 1905 as police forces), and not battlefield units. The charge of Platov at Borodino was a notable exception, but this attack was done in in support of curaissiers (heavy cavalry) of the 1st cavalry corps.
While the cossaks were extremely skilled riders, they did not keep pace with the technological evolution of cavalry. Even back in the 17th century the cossaks were considered an anachronism by western armies. In the beginning of the 18th century Charles XII of Sweden declined the battlefield use of allied cossak units as he considered their usefulness extremely limited. And while their raiding against french forces during Napoleon's invasion in 1812 did a lot of damage, the picture of these forces brought home by the french was of a bow-wielding anachronism.
Therefore I am surprised by the high numbers on this unit, which seems to indicate an modern elite cavalry unit, which the cossaks were not. It also is not appropiate if you look at what the "golden age" of the russian civilization could be, and that would be (probably 1790-1905).
Someone suggested a cheap infantry unit as more appropiate for the russians. I can only concur and also add the suggestion of cheap artillery unit. It was not without reason that the russians were called "The steamroller" in 1914, and the russian ability to raise forces in the face of adversity is legendary.