You obviously didn't read my post very carefully. I said the prohibitions may not be observed by non-Jews, but the positive commandments, such as lighting the candles and the three festive meals, not only may, but may even be mandatory in the Messianic era.
Israel's mission is to compel the nations of the world to observe the Seven Noachide Laws. And those laws forbid complete Shabbat observance, as Jews practice it, to non-Jews.
You're making this way more complicated than it is.
Does scripture tell you this or does tradition tell you this?