If I remember well, it was decided for bosses to have the same stats because CutmanMike didn't want to have to make balancing work. I completely understand, it's hard to do such a thing without it becoming a huge gamebreaking mess. It's even harder to do with 60 characters at once.
Making 60 more weapons would be a serious pain too... but I admit I'd like to see some secondary fire functions. The game as it is already has much more than any FPS I've ever played so let's not ask for the moon here.