You now have the power to make pink horses, unicorns, Batman, Samus, and that creepy neighbor down the street a part of The Witcher 3 with modding. You can find the official home to The Witcher 3 modkit over at nexusmods, with Nexus Mod Manager support.
Here's the gist of what you can change with The Witcher 3 modkit:
Thanks to texture import and export, gamers can now modify the looks and feel of in-game objects, while the possibility of substituting meshes allows to insert new models in the game world in place of existing ones. Finally, access to script files opens up an entirely new array or modification options to many in-game aspects, so modders can fire up their imagination and fiddle with item statistics and much more.
Mods for The Witcher 3 have been slowly created since its release(Note: Nexus Mods says any mod created before the modkit will now incompatible with their mod manager.), but the modkit, as noted above, will allow modders more direct access to change things on a more fundamental level.
It seems that you will be able to do quite a bit with the modkit CD Projekt RED will provide, but there are some caveats. In a Q&A with Gamespot, they mentioned the modkit was "meant for people who are somewhat experienced with modding software and are designed to make creating mods easier." They also specifically mention that this is not an editor.
So what will modders be able to do with the modkit exactly? In addition to creating models, textures, UI, and other visual changes, CD Projekt RED says "players will be able to change nearly every aspect of gameplay mechanics, including creating new, custom skills for character development, adding new features to the game, modifying aspects of enemy AI, making changes to UI, and so on."
Also included in that Q&A was a question about whether or not mods will be coming to consoles for The Witcher 3, this was CD Projekt RED's response:
We are thinking about it but it’s a way more complex process to do this on consoles so we can’t give you any details now. It’s really important for us not to partition The Witcher community and allow access to mods to console gamers, too. We’re considering various approaches to solve this and started initial talks with first-parties about this. We can’t make any hard promises yet, but you can be sure that we’re looking into it.
This is more of a firm maybe than "we are thinking about it." It seems they are actively looking for a way to do it right now but are in too early of stages to promise anything.
You can find a guide to getting started right here on The Witcher 3 forums, which will lead you to four example mods used as guides to the modkit.
What sort of mods do you hope to see in The Witcher 3? Do you plan on modding anything yourself?