Commandments applicable to Bnai Noach
By what precedent does one learn the commandments applicable to Bnai Noach. Ger Toshav or Ger Tzedek? Ger Toshav do not currently exist. When they do exist they qualify as a sub-culture under a larger Jewish culture and population. Bnai Noach qualify as a bnai brit people in their own land. Even though they do not currently exist, because a brit requires an oath to be said before the Safer Torah. None-the-less, should one day this occur and they are caused to exist, this makes them a new creation, like the Ger Tzedek! If Bnai Noach are sons and daughters of Avraham, and Avraham kept all the commandments of the Torah then why shouldn't Bnai Noach honor their father? Honoring one's father is lacking in the 7 commandments.
A possible reason for its omission being that the 7 commandments apply to the ger toshav and the sages of blessed memory had terrible headaches determining if the Cutiim converted from righteousness or from fear of lions.
The Avot had great doubts if the kings of their day still remained faithful to the brit of Noach. Where as in the time of Moshe our Teacher the Torah brings clarity that the kings of the nations had abandoned the brit of Noach. "arose a new king that did not know Yosef" Obviously the government of Yosef was a Bnai Noach government.
The Oath-brit of Bnai Noach: not to do acts of forbidden sex, theft or oppression among one's bnai brit people. The midrash teaches that at the revelation of the Torah, the Ancient of Days asked Esau and Yishmael if they would accept the Torah. They refused. Who were "they"? They were bnai noach! Hence the Talmud teaches that the nations abandoned the brit bnai Noach. Simple logic.
Therefore it seems to me that the precedent by which a person can understand the meaning of Bnai Noach is to learn from Ger Tzedek!