Excellant idea,
Duke John is making a new step by step guide to modding and is posting it somewhere here in the Dungeon. Most of this mod can be achieved through simlpe re-scripting and renaming and with loads of units and buildings already available to adopt and adapt from the VI mod. How to ammend to the campaign map and how to create New animations should all be in Duke John guide. Although if you do create new units you'll need 3ds max, Maya or whichever modelling/animation package you prefer. look forward to future developments.