Just and idea i had for tribe evolution/adavancement where at each level you get to advance in 1 trade or trade related skill. This would make tribe trade that much more valuable.
you can pick to improve 1 of 3 skills.
pick 1 of 3 new or 1 old skill.
-improved weapon crafting
-improved armor crafting
I didnt really give it to much thought just came up with the basic idea, but I think it would help trade if some other tribes have weapons or armor you dont have and you could trade items they cant create for them.