Royal Air Maroc is under discussion apparently. In general though OW had not chosen to add weak regional members anywhere in the world. There are several reasons for that historically including IT philosophy (i.e., one of the stated reasons Air Lingus left). Also there are few African airline candidates that would expand the route map outside of a narrow silo. You would need to add a half a dozen airlines do that and even then it probably would not get you from, for example, Malawi to Botswana every day with reasonable connections and reliability.

There is money to be made in the trans-African airline market but the low hanging fruit is elsewhere.