Swiss guard was just one of the several guards that existed until the XXth century : Corsican Guard, Palatine Guard, Noble Guard, etc.
(A bit like every relevant enough royalty in Europe had their foreigns guards)
While the Swiss Guard was kept thanks to its prestige and professionalism (both of the others were definitely less so), you really have choice when it comes to alternatives : if the ban on mercenaryship and foreign service for Swiss was extended to Papal States for exemple.
As for extra-European recruitment, I suppose that's possible but I doubt it would turn into a "native guard" easily, especially because of the absence of direct link with the pope or pontifical policy.
That said, it could have existed and lasted with the other guards, but by the time these would be disbanded I think that an "African guard" after Vatican II wouldn't be that appealing and may be disbanded as well.