I think we need to focus first on having inner tznius. Meaning- How to be gentle, dignified, respectful, sensitive, etc. Not to be loud, brash, and arrogant. Once we can attain that, outer tznius will be automatic. I don’t think making a foundation focusing only on outer tznius will work.
I agree almost completely with your statement. The one word I would change is “first”, to “also”, because hachitzoniyus m’orer es hap’nimiyus.