I don't understand why a Native American should take offense to this. The lore draws heavily from Native Americans and Dothraki and strikes me as fairly similar to the Subudai. Nomadic cultures in both real life and fiction run fairly parallel. There is usually an outcast barbarian element to these cultures as they relate to more civilized societies.
Honestly man, screw waiting for approval. Just rally your people up and march into the wilderness and make it happen. You don't need approval to get tatted up, ride your horses into the wilderness and live free. Just do it from scratch and there's nothing anyone can tell you otherwise, so long as it all happens through role-play. The only reason you'd need approval for this is if you're establishing it as if it's a pre-existing culture that's been around for a long while with centuries of history involved. If you're starting fresh and establishing the culture from scratch, there's really nothing anyone can say. Start out on day one as the first of the outcasts. Then meet up one by one and form a band of nomads and develop your culture from there. No approval needed, it just happens naturally over time.
Play how you want to play and do what's fun for you and your people. Don't let anyone sit here and nit-pick history lessons, crunch numbers and meta-game judgment. Just go make it happen, keep it within reason and enjoy yourselves.