Well this brings a delima. I'm going to present the two "balanced" possibilities. The shield does stop units and weapons, but the generator is outside of the shield radius. The shield does not stop units but does stop weapons from penetrating from the outside, and the generator is on the inside of the shield (True to the SW universe). Since they've already said that the generators will be on the outside of the shield, I'm assuming they are mostly going with the second one (because they said sometimes generators would be in the shield). Which begs the question why even have them if they only have limited use? About the only thing they'd be good for would be to stop initial artillery barrages, but soon enough the shield will get taken down and your very small advantage gone. Like Cain said: "Why would we build them in the first place?"