well you wouldn't have to import new models or textures for Orks, Elves or Dwarves. Since they are all Humanoid, it would be easy enough to just exaggerate the values that determine character appearance and set it scale of ranges as an ethnicity, using their new ethnicity system for characters that are spawned in for cultures. the most you will need to mod or replace is a colour selection for non-human skin colours, so green, grey, red, etc.
But for an anime model or non-humanoid characters, you will most definitely need to import new models, animations and textures.