Do not want.
Gordon Freeman's (i.e., the player's) experience of the Black Mesa and City 17 worlds are made significant by the panicky, pulse-pounding uncertainty, mystery, and stress of continuously having to find a way to survive in impossible and completely unreasonable circumstances...
Registered just to post on this topic.
I think the OP is absolutely right. The way to do it would be to leave Freeman entirely out of the movie. He should not even appear.* He should be like Sauron or the G-Man or something--relevant to the story but a peripheral character onscreen.
HL2...