Hanging subplots from the first movie:
The cast is jam-packed. Chad, Lupita, Danai, Leticia, Kaluuya, Winston and Freeman all got character arcs to expand upon. All got shyt to do.
- T'Challa adjusting to being King
- T'Challa adjusting to world politics
- T'Challa adjusting to his beef with his father/ancestors post-Killmonger
- Nakia and T'Challa rekindling their long-time romance
- Nakia and her activism goals
- Shuri overseeing the outreach program in the USA
- The future of W'Kabi in wake of his treasonous acts
- W'Kabi's marriage to Okoye
- W'Kabi's best friendship with T'Challa
- M'Baku's reintegrating the Jabari tribe into Wakandan politics
- Everett Ross and the CIA doing CIA things
- Exploring more of Wakanda
- Revealing more about the other 3 Wakandan tribes
- T'Challa and Shuri adjusting to their 5 year absence/post-"Snap"
And that's in addition to whoever the new main villain will be, and his/her character arc. There's literally no room to shoe-in Storm. She's not even the Michelle Obama of the titular character. Lupita has that role and is 2nd billing in the movie behind Chad.
Ultimately, they need to continue fleshing out the characters they established in BP 1, and it should be the responsibility of the x-men director to do whatever with Storm and the x-characters.
Also how the Wakandan people feel about the outreach programs in wake of what happened in Civil War (medical staff dying via crossbones/wanda).