I like this mod! I like that it is based on Earth nations, this remind me of Aurora (a very geeky space simulation) where there is Russia, USA, China, Europe Union in the Space race.
A few remarks. Cosmetic one: it is sometime difficult to spot the pirate's grey color. Perhaps something like whit/brown? Also, why ISA is not Blue in color? :-)
I think the mod would be even greater if there was not one but several space stations on each side, with some traffic and convoys sent or returning to these stations. Perhaps Barnard Star is a system with vast riches in minerals, so some mining stations would be the cause of such convoys traffic, with escorts on both side, the pirates in the middle!?
Also, do you have some plans for exceptional events, like in Xplo mod? A rare fleet appears, very strong, for a specific mission, then go away. Perhaps it can even be the aim of the game, defeat the fleet and you get a message that the faction you supported will now have supremacy over the system (basically you 'won' the game, even if you can continue playing).
About gun calibers, I find them too small. 3 Inch caliber is very small for a space ship, during WW2 the gun of tanks were up to 122 mm and more, so imagine a spaceship. Battleships had 406 mm guns, and a world war II battleships was perhaps as small as a space destroyer! So here, even if this is just cosmetic, I think you should up the calibers.
As for game balance, why the Piranha SRM costs 240 credits and is such a crap, compared to the Stinger that does more damages and cost less?