[JoeGuardsman]

One squad cannot pick up another's weapons. That rule is referring to other models in the squad that carried the weapon.
I also find the dilemma inherent in support squads. You have very expensive units of 6 guardsmen and begin taking really serious hits to your effectiveness after 4 casualties. It can be very difficult to prevent damage to that. Luckily a lot of people just shoot at the closest squad half the time but savvy players can kill your points sink.