(In this case, I will point out that the plural of strelets is stresltsy, to help differentiate a plural since the singular term ends in an 's').
I ultimately included it just to have something different for games that include black powder weapons. Lastly, the strelets was another archetype that I wasn't sure whether to include, primarily because they were mainly known for being infantry sharpshooters with harquebuses and other early firearms. Most of them were depicted as high-level lawful good fighters. Again, going back to Dragon magazine, in issue #53, there was an entire article providing 1st Edition stats for several famous bogatyr characters from mythology.
The bogatyr are classic heroes from Russian folklore and mythology, not too unlike early edition paladins. In the end, I decided that my list was a 'fantasy' version using the various sources as inspiration rather than attempting to portray them realistically. I did waver back-and-forth about whether to include the Cossacks, since they are a 'real world' culture and I wanted to make sure that I wasn't portraying them incorrectly.
FIGHTER: As expected, this class was one of the easiest when it came to developing subclasses.