Ludwigp, I can only say from my own view point, but if this was my game I would not touch the native american aspect with a ten foot pole. You have to understand that this is a small team of developers - if **** went down legally for miss representation then it could end all of this. Even AAA game companys try to stear very wide around anything like this.
You have plenty of gear to go RP. In fact it has been done before to great effect.