A book by Orson Scott Card. An interesting read. Possibly a VERY interesting LA Mictlan/Marignon mod.
WARNING:
This thread will probably contain lots and lots of spoilers.
http://en.wikipedia.org/wiki/Pastwatch
I don't have that many ideas for the actual nation or units yet, but heroes would be easy:
Cristoforo Colombo,
excellent leadership, good standard effect, old age for a human, some Holy magic, perhaps some magic he has learned from his wife, "Sees in the Dark".
"Sees in the Dark",
stealthy, has a "magical staff" with long range, prec 100, 2 ammo/battle, uses strong paralyzing poison or just causes 150 unresistable fatique. 'Bang' sound would be nice. Has some Nature magic, darkvision, can heal afflictions.
I don't remember the proper name of the "Scarred King", but he would be a high-level priest, and perhaps have sailing or something similar. Perhaps he would generate fire gems, with his solar-power light being explained as a source of both his priestly powers and power over fire magic? "He holds a mystical talisman capable of bringing the light of the sun to the battle, encouraging soldiers and raising faith in the new god." Perhaps Fire 1 as well, it'd make him very similar to MA Marignon Inquisitors, which would be a nice addition.