Hi Stuart, and thanks for answering to my question! Now I think I’m ready to play a game, finally!
Regarding the Commonwealth question, on the rolebook there’s an intro saying that they will not allocate a rule to each nationality. So, I think it’s not important who was thoughest, or faster firing with a weapon, but you can choose a rule for a specific Commonwealth force based on an appropriate historical lore of that Nation, at your own discretion.