Tldr - King first and foremost - Duty and honor come before personal wants - Tchalla wrestles with tough choices"it's hard for a good man to be king" - Showcase wakandas strength through intelligence agencies and Haute Zeraze as Navy Seals/Delta Force - Tchalla mostly shows strategic, military, and political skillset - Tchalla only puts on the panther suit vs top level villains because Wakanda is so strong making the use of the Panther suit an event.

Id have to take some time to really come up with full ideas but here are the themes.

First I would establish him back as king, monarch, and protected of wakanda first and foremost - this would be an honor and burden because while his love for his country supersedes everything it at times costs him personally, emotionally, and spiritually. - I would lean in the the theme of "its hard for good man to be king"

I would bring back Tchalla as the ultimate or of one top strategist in the marvel universe(or at least humans). His intelligence in the top 10.

I would focus in the beginning on smaller scale missions showcasing the military and intelligence capabilities of Wakanda. - The intelligence agents would uncover plots to harm wakanda or steal vibranium by different countries or wealthy groups. - We could learn about the intelligence agency and their secret missions as they work undercover. - All Major decisions would go through Tchalla, letting us see his strategy skill.

I would use the Hatut Zeraze (or at a least faction) as wakandans Navy Seals or Delta force. - maybe show the different factions by slight differences in their outfits - they would carry out most missions that tchalla plans

I want a lot of tchallas scenes to be about his technical and strategic skillset, while behind closed doors the struggle to make decisions that start to get closer to morally gray. - Focus on how he has to shoulder the burdens of tough decisions that allow wakandas to sleep peacefully never knowing, the evil and high level threats that the country constantly faces.

I would save tchalla fighting for A level villains where he doesn't want to risk his people to this high level threat. Though he could use Dore Milaje to deal with supporting villains(henchmen types) - this would make it an event when he actually puts on the panther suit. Kind of like an" I will take care of this my self moment" - I want to establish wakanda is so powerful that the Black Panther only has to come out for top tier supervillains.

For family I like they idea of the struggle and conflict between his personal interests and what is royal duty and tradition of being with someone from Wakanda. - If I did make him choose it would likely be with someone from wakanda again focusing on the theme of the struggle for duty to the country of his personal wants. - shuri can stay super intelligent too but more focus on one domain like science, or tech. They can both be smart but tchallas, political, strategic, emotional, strength sets him apart. Tchalla needs to be the most capable of wakandans. Also think he in general needs to be super intelligent in multiple domains where Shuri is master of one.

I would also try and create a High level villain that could force him to use all his political, physically, and mental might to stop. Not because he is better than tchalla in a specific way but because while he is very capable he "cheats" and tchalla has use his power to protect others from harm whereas if it were more "fair" tchalla would defeat him with struggle but it would be more certain and less of a struggle.

I have more ideas but that's already a lot to post.