Would the people who feel strongly about their racial uniqueness be ok with the unlocked versions being awarded after a quest with some lore about that race? Because that would be sort of awesome.

(Good luck writing a lore quest about my Elezen long johns, though...)

I don't see the current lock as increasing diversity at all. Some of the hempen sets are popular and often seen (e.g. Miqo'te female, Highlander female). Some are pretty great. Others are less great and nobody equips them; for some unpopular race/gender combinations I'm not sure I've ever seen some of the hempen gear at all. I really don't mind anyone else having access to my Elezen stuff even though I use the top quite often; the more the merrier!