With the current possibilities of Event and Regional
Decision scripting one cannot really write the RGD's to work sensibly. In addition, Indian elements all have the exact same faction (IND) until they are taken over through one of the major factions, when they take on that faction's designator.
The only way to assess whether an element actually is 'Indian' is by assessing the element's Attributes parameter having '#IsIndian#', but you still cannot assess whether the element is an enemy element. This is why so many of the Indian RGD's reference whether the target region has an Indian village, because an Indian unit with the USA or CSA faction tag cannot enter such a region. But you can very often find Indian units away from villages, and these will be invisible to the current RGD's.
Indians really should be a complete set of different factions. The term 'Indian Nation' really is an insult to Native American peoples, even as it so 'gracefully' insinuates a sovereignty of these people, it in the same breath designates them as all having the same nationality. It would be like saying all Europeans belong to 'The European Nation'
Without the necessary script commands--at the very least--and realistically represented Native American tribes, I would not look any closer into using Indian RGD's. The only one which would have been really useful is Subversion, and it doesn't work. If it did, the others might also come into some importance, but otherwise they are all pointless.