Shaders are located in Engine/shaders.pak. Thanks to that, you cannot create a “standard” mod that modifies shaders, as mods only work within the Data/ folder. Instead you will need to provide your own shaders.pak and shadercache.pak, which the users will have to manually place in their Engine/ folder.
Modifying shaders.pak is trivial, just change whatever shaders you want within that archive. Then you need to generate shader cache:
Tools/shadercachegen/system.cfg to rootEngine/shadercache.pak, Engine/shadercachestartup.pak and Engine/shadersbin.pak (or just change their extension to something else than .pak)Tools/shadercachegen/ShaderCacheGen.cmd. This will approximatelly half an hour complete (you can check shadercachegen.log for progress, it will have around 110 000 lines by the time the process ends).Tools/PakShaders.bat from root directory. This will create new shadercache, shadercachestartup and shadersbin PAKs in Engine/ folder, containing your new shaders.system.cfg from backup