Well I had some better leg positions originally and then I discovered that the shooting animation is a upper torso only animation. That means that no matter what I do with the legs they will use the legs animations from Both_stand1 or run/walk1. So I wish I could implement my origianl legs or your suggestion but it wouldn't matter. And I don't think altering the code to support the new legs is worth the work for the coders. Their time is better spent on features and bug fixes.
I shot guns IRL for the military. Well I did shoot guns, I'm out now. But you do want your arms straight when you shoot. If your arms are slack the recoil will be more pronounced and that will mess your aim up. So that's the reason for the straight arms. Hope you don't mind.