why do you think Shephard should have anything to do with Half-Life again? He is the player character (YOU are shepherd). Don’t we have our hands full already with ONE silent protagonist (aka Gordon). People scream about anytime someone mentions him talk in a hypothetical movie script.
If anything you can pretend you are Shepherd (and shut your ears when NPCs mention the name “Gordon”) when playing Half-Life if that makes you feel better.
Seems like you guys have substituted Adrian Shepherd for something more substantial and important, like there is a need for something more in Half-Life saga but you can’t put a proper name on it. So Adrian Shepherd has stepped in. That is just sad really.
EDIT: You guys have seen too many movies where someone on the enemy side (in Half-Life’s case HECU are the enemy as long as they are out to get you) has an interesting aspect to him and you think there is more than meets the eye.