As far as taking on Jewish customs, please note that the idea of "voluntarily taking on" mitzvos from the list of 613 mitzvos with a few exceptions, is based on the Rambam's exposition of Noahide law. Other authorities, such as Rabbi Benamozegh, describe Noahidism differently. They imply that each of the 70 nations has its own "mitzvos", its own unique way to serve G-d. If a national faith were to be divorced from idolatry and adhere to the seven laws, it would be more appropriate for a non-Jew to follow their customs than to adopt Jewish ones. In fact in an ideal world, a non-Jew would be obligated by his or her national faith, just as a Jew is obligated in theirs. According to this view, a BN Bnei Noah is discouraged from taking on Jewish customs (although they can learn from them). For this reasons, reason Judaism doesn't seek proselytes , because non-Jews have their own purpose to fulfill, and proselytism interferes with this.