I think this would be a great opportunity to put a couple of African factions in. Slavery pretty much made the colonization of the Americas possible (US, Brazil, Caribbean). All the important european powers dealth with African states during this period (1700-1800). I read that there will be like 50 additional factions, so there is no reason you can't have a handful of factions in Africa. I recommend just 6. All fought with guns, all had coastal navies and most importantly they were all empires...

Morocco (in Morocco of course, premier north african state)
Tripolitania (in Libya, fought the USA)
Kaabu (in Guinea, sold lots of slaves to french)
Asanteman (in Ghana, sold lots of slaves and gold to English and Dutch)
Benin (in Nigeria, sold some slaves and textiles to Portuguese and Dutch)
Aro (spanned Nigeria and Cameroon, sold lots of slaves to English)

I'd also expect to see some Native American factions, especially in New England and Canada.