“Working on ones inner tznius is wonderful, but that work doesn’t exempt compliance from outer tznius at the same time. If one pushes off one for the other, they risk never getting to the latter.”
While this is true for some things, I don’t think it will work for this particular issue. I think in order for people to accept the rules and requirements of outer tznius wholeheartedly, they must realize its essence and accept it with love, not confusion or contept, and the best way to do that is by first becoming a person with inner tznius. A person that has attained true inner tznius will realize the holiness and beauty of dressing outwardly as a servant of G-d, and will do so by their own will. Not by being FORCED to.
Also, I think tackling one issue at a time is better than two at once. We don’t want anyone to just give up the whole thing. And if there should be an order, it should be inner tznius first.