In all fairness your cobra blueshirts looks much more modern than the 25th blueshirts Sonnilon.
This is how I see it in my Joeverse.
Ak's are good enough for the 25th blues allthough I buy the ak's with metal folding stock so they dont look completly old.
My ide about vipers is that they are former millitary that has been recruited by cobra and as such they use the weapons they trained with in their respective armies. An american viper would use an M16 and Norwegian viper would use a G3 and so fourth. Viper would also have a varity of weaons in their squad and even specally trained Vipers with special equipment. Blueshirts are just regular ahem... Joes and as such are given a minimum of training and the cheapest gun available in the region and thats the ak more often than not. Blueshirts also gets training as snipers whereupon they use the dragunov, their sniping tactics have made them feared as the most professional terrorist group in the world, however their sniping tactic is next to usless agains the elite force GI Joe where every member are experts in finding and dealing with snipers or atleast have the means to do so. Cobra drivers gets the scorpion machine pistol.
One trooper I wont buy for my joeverse is the 25th cobra bazoka trooper a regular Viper or a blueshirt can carry one.
All in all I try to follow the filecards as much as I can, the file cards are a very good inspiration.