That doesn’t really fit HL that well though. Sure, there’s combine tech, but it takes place in a world where resources are short and you use whatever is available. It would be nice if HL3 had some new weapons to use though. As long as all the weapons weren’t like that.
Black Mesa doesn’t exist in real life, but it doesn’t in the game. Why can’t the same be said of a weapons manufacturing company? Gun-Nut manufacturing co. doesn’t need to be integral to the plot, but it would explain an MP7 knock-off with a 45 round magazine that shoots grenade rounds.