...and unlike Hideous Destructor it looks like you actually made some effort with regards to balancing. XD Pretty awesome mod.Perhaps rarely among gameplay mods, Mutiny actually makes maps harder. Although you'll have plenty of ammo, since the marines drop their guns when they die, and the enemies generally have less health (although the bigger robots have a lot of HP), the enemies move faster, hit harder, and many of them have hitscan attacks.
Baron replacement seems a bit on the weak side though, while the mancubus replacements seem a bit high.
Bugs: Punching enemies just leave their arms extended during melee (you just hear their punch sound and get hurt but don't see them do anything); the medic plays the pistol sound when he punches; the plasma guys' deaths don't trigger the last script in map07. Ceiling turret also doesn't have sounds.
That said, I'm quite pleasantly surprised that a fastchase monster could be made into such a decent low-level mook like the officer. Fighting groups of them sometimes feels like a choreographed ninja fight.
Feature suggestion: Maybe you could make the GL fire a bit further than the hand grenades lob? It seems kinda odd to have a launcher for something you can do with your off hand (the characters are throwing with their hands right? ^^; )
Also, I think the commando might unintentionally(correct me if I'm wrong) be one of the best "buddy" monsters I've seen. They give you ample warning to get out of the way before they shoot, don't race ahead of you and into your line of fire, focus a lot of firepower on very specific targets, and the jolly fat dude act has just enough personality for me to think of them as something more than just some thing-that-also-happens-to-damage-enemies.