Hey!
Nice idea, if you need any help I am a native reenactor and study/write on native and colonial interactions in North America.
There are, however, many problems with creating a mod like this- the first huge one is that it is almost impossible to recreate native warfare using the MTW VI engine.
However, on historical accuracy, graphics, maps and sfx let me know what help you need. I would suggest you aim for a much smaller mod at first- perhaps only focusing on Central America or Northeast America. It will be VERY difficult getting together both portraits and unit graphics for all the different cultures.
Thanks!
Justin