I was originally going to /newstuff this as it was, but I decided to get some more opinions before putting it on /idgames. The Mutiny Mod was originally going to be the base for a series of hubs, but I decided to make it a gameplay mod for regular Doom maps while retaining the potential for it to be used in its own level set. The Mutiny Mod replaces all monsters and many weapons and items, and adds some of its own that a level author could use to make a map for the Mutiny Mod. Your enemies consist of various space marines, robots, and vehicles. I wanted to make the marines a little less predictable than the typical Doom monsters. As well as shooting you, they can punch you and throw grenades, and some use A_FastChase to circle strafe you. You have a full inventory a la Heretic with carryable medikits, powerups, etc.
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. Some maps, especially very large open maps or Hell Revealed type maps, may experience a greater increase in difficulty than others.
Screenshots taken in the map Jagermorder 01: Chemical Lab by Afterglow