In another step towards virtual global dominance The Creative Assembly and SEGA have announced and released a comprehensive SDK to the community in the name of all things mod-like. Among the several touted development tools is Steam Workshop integration, allowing the easy and widespread sharing of new custom maps, historical scenarios, and modifications ranging from minor through to total conversions.
DAVe database tool - used for editing database entries
Unit Editor - for changing the look for units
Tooldatabuilder - for unpacking data
Campaign map reprocessing
Max export scripts for models
Example Max files for most model types
BoB processing tool, also capable of building mod packs
The Shogun 2 Assembly Kit can be found in the Tools section of your Steam Library alongside the previously released TEd, map creator. Now excuse me while I eagerly download the Assembly Kit and attempt to have some fun modding.