Well I reached the end of the content and I'm still not sure what either intelligence or agility does. For the opening prompt it might not be a bad idea to state what each stat effects, and if it's actually does anything in the current build, and maybe include the stat bonuses for the starting options in the descriptions somewhere. Also going to throw out that save scumming is almost necessary to be able to stop the tribe from instant losing, as they don't raid on their own. Perhaps give the player a week grace period to build up stats and learn how the mechanics work before you start getting raided. You should also have when an enemy tribe raids you be it's own separate screen, instead of something that can randomly pop up whenever you load a save or do an action. Like for example, right after you went to sleep for the day, it'll go to a screen saying your tribe got raided(or didn't) what you lost(if anything), the videos and then a button to continue to the next day. This would lower the extreme need for save scumming, as if you're unlucky you'll be raided by a tribe for every action in 1 day.(It happened to me once.) Successful repelling of a tribe should result in extra booty too, since it's likely that they had tools, weapons, and some food before they raided your tribe and you should be able to grab it as a spoil of war, as it stands repelling a tribe just gives you nothing, and you lose nothing.
Anyway here are some future ideas that might sound good to you.
1. Diplomacy, tribal warfare just like any other had agreements that you could choose to honor or not. By signing a truce you can prevent raids from a tribe in exchange for influence or maybe a tribute, conversely if you've been hitting a tribe hard they might offer a truce via tribute as well.
2. A scouting system that lets you gauge the current strength of a tribe, right now it's completely random but you're not going to want to keep this for the future.
3. Let the AI leader do raids themselves before you become chief, and let you participate in a raid yourself boosting the strength of your raiding party by using your attributes.
4. Massively expand pre chief gameplay, as it stands for a week you just pray to the gods and train with an odd successful hunt every now and then, I wouldn't trust that guy in any leadership position with his credentials. Make it so that you can get the chief position in a few other ways, either by leveling your influence,(Current method) challenging the chief to 1v1 combat, or straight old assassination and some bribes.
5. And finally trophy wives, they do sorta exist to begin with but they don't do anything. Perhaps you can after a large amount of dicking, convince them to fully convert entering your harem providing you with bonuses against their original tribe, ranging from a bonus against(and for) raids to unique technologies related to their faction that you couldn't get normally.