I know this is ancient, but I thought I'd add something I've done several times and enjoy each time I do it:
Create a custom nation that encompasses Granada, Tangier, and Marrakesh. If your capitol is one of the provinces in Granada, you get the benefit of being on the Eurpoean continent, so you can make Trade Companies in Africa that feed into your trade capitol of Sevilla. A usually make the culture Leonese and name the kingdom "Nova Asturia," fantasizing that a monastic order called The Knights of Asturia partook in the Spanish and fictional Moroccan crusades, winning Granada, Tangier and Marrakesh from the Pope. Over time, the needs of a society simply couldn't be met by a monastic order, and so they somehow chose someone to serve as their king.
I like playing this way because it makes colonizing the Americas possible earlier in the game, ahead of some of the competition, and because Western Africa is pretty weak. If you get lucky, Tunisia and Tlemcen don't ally with the Ottomans, so taking their territory isn't too difficult. One thing to note, however, is that when you do this there are really only five kingdoms that would readily consider you a rival, and it's random which three you'll end up with: Portugal, Castile, Aragon, France, and England. If you can ally with either Castile or Aragon, you should be okay, but if they both rival you it could be exceptionally difficult. Having four Iberian kingdoms is a pretty cool way to play either way though.