We are keeping it fantasy but I think we are going to push for each faction to replicate a major country from the era. Unfortunately, there are no plans to represent native americans at the time - but It could easily be a feature we could include. I'll see what the team thinks about it
Im not lover of the exotic troops, but can understand why somebody may want it.
For me best way to add them is make some lesser mercenary factions, with first troop recruitable from tavern, and rest available by upgrade (should be easy to do when using module system).
Adding them (native americans , asians itp) as nations my not be practical, they will need probably to much creative troop making
(ex westernized aztec warriors or samurais in plate armors, armed with war hammers
) to balance them against other nations.