It's always good when a major franchise decides to add (or re-add) mod support. This time it's Call of Duty. Treyarch, who developed just under half of the titles in the main series, will bring the feature to Call of Duty: Black Ops III for the PC. An unranked dedicated server will also be available, because ranking players using modded content is not exactly… fair… for any reasonable mod tool set, across all possible creations.
They intend to allow custom maps and game modes, which leaves a few open questions. Are custom assets a part of “custom maps and game modes”? What sort of scripting options will be available? Does this mean that users cannot add custom weapons (or even vehicles)? Then you can get into more specific questions, like HUD possibilities and such. Thankfully, we have enough options for “Total Conversion” mods these days, with Unreal, Crytek, Unity, and others letting just about anyone access top-tier tools, in a variety of languages and platforms.
Treyarch is planning to release a closed alpha of the mod tools in March.