Regarding S America, look at Lopez surviving and prospering in Paraguay - IIRC his regime was a blend of Spanish and native, and he spoke both languages etc
I did something similar in a story I once began, where West Indian troops rescued Britain from Napoleonic domination late in the 19th century, and mixed race marriages became a symbol of patriotism
One wonders from that whether mixed race nobility could have a part to play in earlier ages ?
Best Regards
Grey Wolf
I made a rough timeline for a successful Frankish Outremer that ended up streching down the Red Sea. An Ethiopian kingdom, probably ruled by the Zagwe Dynasty, would develop and get into communion with Rome. The Ethiopian royal family would intermarry with Frankish nobility and royalty, and in the east a much more mixed race nobility would appear. The extended Frankish occupation of the east will lead to larger commercial networks as the Italian merchant states link directly into the pre-existing Arab trade networks that lead east to India. I think that Arab merchants would begin to convert to Roman Catholicism in order to do business, and those converts would be able to start running their own trading houses to do business in the east. These converts would be able to get wealthy and start marrying into the Outremer nobility, ala the Italian merchant princes.