I know that there are already mods which can do that. But those mods are all based on units which are only playable in campaign. Mods usually don’t include any new units since you’d need to do 3D models of them. Also there currently just arent enough models ingame to find a non-EU replacement for every unit. In addition, you can’t play in multiplayer with these mods.
This DLC would be strictly optional for people who, like me, are fed up with recruiting European-looking swordmen or pikemen as Aztecs or Chinese. New modeling work would be required since we need a variant for every age and there currently aren’t enough models ingame as stated before.
If work is done nicely and the units fit well into the rest of the game, I am willing to pay for it. Devs, just give it a few thoughts. After all, this game has a relatively large community and there’s a lot of opportunity you’re missing out. But just to be clear: I don’t want an ingame shop where you can buy skins separately for horrendous prices. That would be a no-go.
Of course a free mod would be even better but everyone should be rewarded for their work.