Yes, sure I know the word "gaijin". It's a well known part of D&D lore, ever since the 1e Oriental Adventures.
I can see the appeal it has for you. How about if "Free Legion" is the official name of the group, but a lot of people including members of the group call it "Barbarian Legion" informally? After all, while most members are foreign, it is not exclusively so.
Okay, I'm fuzzy on what's going on. Who operates and/or controls this 'sorta Foreign Legion?' It sounds like y'all are putting it under the auspices of the Eternal Empire, but that seems a little odd to me. Would the kingdom of Rauland allow a foreign power to plop an army literally right on its doorstep like that?
Or am I completely misunderstanding the proposal? I feel like that is a far more likely interpretation.