You could farm floodplains until you grow to a decent size and then replace them with a Kasbah. And 1 food for a production and gold is pretty useful. Though spamming them will hurt your ability to counterattack as the AI will get the fort bonus too.
I think an interesting ability (missed opportunity) for the Berber Cavalry in lieu of the friendly territory bonus would be to receive defensive bonuses. That way there's synergy with all the Kasbahs that will be covering your territory.

Gold and + 1
per International Trade Route... And how, exactly, is Portugal THE trade civ?
To make up for this, Portugal would need 6 different luxury resources in a single city for it to have a chance to ever reach this level, and even so it would not get the culture bonus!
I'll be sure to give them a chance! Love the achievements, by the way!