For BP 2, they should introduce T'Challa's half-brother Jakara Son of T'Chaka who was raised abroad and make him Black Planther as Queen Shuri deals with the major outside threats.
Jakara is soon found out to be a member a Wakandan terrorist group called the Hyena Clan who plan to steal from the Wakandan Reservoir. Which causes Queen Shuri to finally step up and challenge him for the Black Panther mantle.