Hey, I saw you were going to make a mod about the Sami people. I loved that mod in civ 5, but I think the decision to use a made-up leader for them was not the best possible. Especially in civ 6 where the focus on leaders has moved from representing the entire civ more into showcasing an interesting leader or a period of time from an era, I think you should give them a new leader this time around.
I am not of Sami descent myself, but I have studied their history a little bit, and I have two interesting leader prospects to suggest. One would be Akmeeli (Ikämieli in Finnish), who was a chieftain in the Sodankylä area in the 16th-17th centuries. His life is covered in legends, but it seems like most historians consider him to be a historical person. The legends tell that he was a mighty shaman, who could travel through the world by assuming the shape of wild animals, like fish, wolves, bears and even birds.
Another story tells of the arrival of Finnish fishers and lumberjacks to the lands of Akmeeli's people. The Samis had lived using sustainable methods, but the newcomers, using their superior fishing methods and technology, started to put strain on the ecosystem. Akmeeli, being in harmony in nature, called the forces of nature to fight against the Finns by making driftwood suddenly turn into dangerous, giant fish, and by killing their cattle by making them eat balls of reindeer fat with iron spikes inside. My sources for Akmeeli are Finnish web pages since I'm studying abroad and can't access printed material, but I'd love to take a deeper look at Akmeeli if you are interested. Almost all sources I could find are either in Finnish or Sami (which I can't understand). Of course most of these stories are obviously only legends, but does it make Akmeeli any less interesting?
I could think of several interesting uniques for Akmeeli. His agenda could be, that he hates leaders who remove natural features or harvest resources, and likes those who build natural parks and plant woods. His trait could give a bonus yield for bonus resources (making the player less inclined to harvest them). Another neat thing would be to make certain resource tiles around a city always visible or automatically revealed (to reflect his ability to assume the shape of these animals). A simple design for Akmeeli would be something like: +1 faith from bonus resources, and automatically reveal all tiles containing fish, whales, deer, furs etc. from 8 tiles around a city.
The second leader prospect would be Snøfrid, daughter of Svåse the Finn, who was a princess of a Sami tribe somewhere around Norway or Sweden. She married the Norse king Harald Fairhair, and their story is told in a ancient Norse saga, which I found translated here:
http://www.sacred-texts.com/neu/heim/04harfgr.htm. The story tells how Snøfrid seemed to enchant the king, so that after meeting her he no longer cared about ruling his kingdom. Since most of the material about her seems to be in Norwegian I can't help much on her, but I think she would make a pretty interesting leader.
Her uniques could be related to how she seemingly enchanted the king, perhaps influencing him to make decisions in a way that it was she who was actually in charge. Maybe she and the target civ could get an extra bonus when a diplomatic mission or an embassy involving her is made (to reflect her status as both a princess of her own tribe, and a queen of the vikings), and she would get no warmonger penalty for declaring a surprise war (but penalties for capturing cities would be normal; to reflect her subversive, enchating side). Her agenda could be that she doesn't mind those who declare surprise wars, and she likes to send diplomatic missions. Since the sources of her come from sagas and legends, these uniques are not very accurate historically, but I do think she would make an interesting leader. Additionally, more research on her is needed to see if she'd have other sides that could be implemented.
My only experience on modding is creating new city-states in civ5, but I'd be eager to learn more and help with the Sami, since I'm also planning to do my own mods for civ 6. I loved to play a nordic map in civ 5, and having two Sami leaders would make it so much more interesting, especially since they influenced different areas and eras!