I have an idea about the other races being a big part of the Kuriotates.
Basically there would be around seven other races, and they would all replace various parts of the Kuriotates unit tree.
Races:
Naga-Replace the dark recon units(assassin, shadow, saboteur)
Centaurs-Replace most of the cavalry units(horseman, chariot, war chariot, war elephant. For these use the stats, not the idea of a centaur on an elephant.)
Eaglefolk-Replace the rest of the cavalry units(horse archer, camel archer, knight)
Giant Wurms (the guys from Magic)-Replace the siege weapons. Warious large worms. These guys will have greater normal strength and less bombardment strength than normal siege weapons.
Satyrs-Replace some archer units(longbowman, flurry, marksman)
Merfolk-Replace the combat naval units. This includes water spellcasters. They do not replace naval transport.
Giant Turtles-You guessed it, they replace naval transport ships.(these two races will not work until we have a more complex naval system)
How does this work?
there would be multiple "centaur units". Normal units would not be upgradeable to them and they would not be upgradable to other races. For example, a scout could upgrade to a hunter but not a centaur horseman. Then that hunter could upgrade to a ranger but not a naga assassin.
What do you all think?