Nations of Earth is an empire theme, not a commander theme. It's a set of ship classes names and ranks.
I wish commander name themes could be mixed in-game too, so you could have say a spanish first name with a german last name. I know the United States commander theme can do that but it still largely outputs English-american names.
If I remember correctly, in C# players will be able to create commander themes, do you could just make a custom theme that combines the first and last name pools of whatever theme you want. Doesn't help if you want separate pools though, which I imagine Lucifer does since he didn't mention combing pools, just wanting the ability to use more at once.
