Yep. Multiple tribes of masklings are generated during world creation, and they view each other as enemies. They'll usually have different colored robes.
I've noticed tribes having multiple settlements, but also there being multiple tribes with the same color. This can get reeaallyy confusing. Could you look into making sure maskling tribes can't have the same color? Or if they do they're all one big group?
AI Tribes pick randomly from the available colors, sometimes there just aren't enough to go around.
Yeah. It would be neat if there were larger tribes with lots of settlements, and then there would be larger battles between tribes.
Also, is there a plan to throw in a DF-like option to abandon an empire and then still have it in the world to interact with?
That would be an interesting idea, but it could be tricky for game balance. The world grows over time, so a player starting fresh in an old world would be at quite a disadvantage.
What if your new player empire were able to send nobles bearing gifts to other empires that you'd made before? Politics would be a neat expansion.