First I would cameo 18-20 year old Ororo in a BP movie, just for a hot second, to bring in the audience. Okoye is informing T'Challa of a monstrous storm developing just across the border in Kenya. They both go to investigate.
As for her solo, I would give Ororo the Aquaman treatment. Full origin with action/adventure/fantasy elements, even a touch of horror. I'm not going to do a full treatment, but basically tell her origins, starting with the story of her mother's line as protectors of humanity from the Shadow King, being orphaned in Cairo, becoming a thief with Achmed, picking Xavier's pocket which leads inadvertently to SK being sealed away in the Astral Plane again. About 10 minutes.
Then her growing up to about 11 and leaving Cairo, almost getting raped, killing the would be rapist(who is being controlled by SK) and swearing never to kill again, and then her powers manifesting when she almost dies of dehydration in the Sahara. She flies the rest of the way to the Great Rift Valley and meets her grandmother, who somehow knew she was coming and is standing on a cliff or whatever. She is taught the history of her people and how to control her powers. She brings rain to the people in the region, and protects whom she can. Some of the people even worship her as a goddess. Another 5 minutes.
Flash forward to her at 18-20 years old, present day.
She's in the jungle, flying around, smelling flowers and eating fruit from the tree tops, playing with birds and monkeys and butterflies. Total nature goddess moment. She hears a drum calling her back to the village. She meets with her grandmother and some of the other women of the village to plan her day. She is to do so and so, but Ororo is preoccupied and her mind wanders. She is chastised by her grandmother, who is Queen, but if Ororo is to take the crown one day, she must so and so.
Basically short of the long, use Shadow King as a background motivator(he can still influence people from the Astral Plane in their dreams and such) of Deluge, who in classic MCU formula, has a similar power to the main hero and is mean from a bad childhood, and Ororo must override his continental-sized storm, with some SK-controlled slavers as the b-level villains. BP and Okoye guest star when the huge storm threatens Wakanda and all of the continent, and they fight some of the slavers and help free hostages while Ororo confronts Deluge. Eventually she overpowers him and saves all of Africa. BP and Okoye are impressed and they talk to her a bit after the fight, offering her a place in Wakanda. Young Ororo might even flirt with the older man, but she is too free-spirited to settle down just over the border.
Mid credit scene has Xavier in New York. Cerebro has been following Ororo and her recent huge display of power. Scott busts through the door saying the X-Men are gone. Xavier says power up the jet.
Final credit scene is Ororo helping some villagers clean up after the megastorm from Deluge. Just as they are finishing, the Blackbird lands, Xavier rolls out and says her great power is needed all across the world. Ororo looks up with a smile on her face and says 'let us go then'.