A secular couple's wedding

A. The bride and groom can open it, since it is unlikely that the prohibition against wine was stated for the person himself (is it forbidden for a person who does not observe Shabbat to open wine for himself?). There is no obligation to distance the person from himself. Unlike just wine, with regard to a wedding wine, one must discuss it, since wedding wine is a prohibition against hafza and wine is forbidden against hafza, and therefore, apparently, it is also forbidden for the person himself. And one must be careful about this.
on. The requirement for the witness to be observant of Shabbat even though the groom is not does not seem problematic to me. This is a requirement for a kosher witness (and as is known, this is evidence of the observance of this). There is no requirement that the groom be observant as a condition for his kiddushin to apply.
third. Therefore, I would not relax any binding (preventive) halakhic requirement. In requirements that are customary or something that does not prevent, there is room for relaxation even for religious people.
D. My system is that the commandments of a person who does not believe in God or in the status of Mount Sinai are not commandments and his transgressions are not transgressions. I was asked in the past how his kiddushin is valid, and I answered that kiddushin is a contract. Whoever signs the contract is obligated to it (he says that he is obligated according to the Law of Moses and Israel, to everything it says, even if he does not know what exactly it includes). The commandment of kiddushin (to the extent that there is one, I think it is very doubtful whether it is also a mitzvah in the Rambam), of course the groom does not have such a commandment. But the contract was made and it is valid.
the. I wouldn't preach to a secular couple to get married as a "Dmoi". I'm not sure that there's much value in that. But if they want to, there's no reason not to hold such a ceremony, and it should be done with all its details and grammar.
and. On the other hand, sometimes such couples demand equality. Just this morning someone asked me about the bride's additional signature on the ketubah. I told him that I don't think there is a halachic problem with this, but I don't understand this egalitarian trend (like the groom receiving a ring, and having the bride secretly twirl a woman's hand twirl it by a man, etc.). After all, the ketubah is a commitment from the groom to the bride, and not vice versa. It's not equal. So if the bride also signs, will it become equal? ​​Equality depends on the essence and not on the ceremonies. On the other hand, the desire for the bride to give a ring is also nonsense in my opinion. The act of consecration is completely egalitarian, since the consent of both parties is required. The form of applying ownership is that the man gives a ring. But it's a ceremony and not something substantive, so I don't understand why it bothers anyone. Or alternatively, if the bride also gives a ring, will it change anything? All of these are scrambled trends that lack any taste or smell.
In short, whoever wants a halakhic ceremony should accept it as it is and not confuse the mind. As for the rabbi of the wedding, in my opinion there is no reason or justification to change anything. Halacha is Halacha, and whoever doesn't want it shouldn't buy it.
As mentioned, there are requirements that must be discussed halachically, regardless of secularism. Writing the ketubah in Aramaic. Various circumambulation ceremonies. Only men recite the seven blessings, and more. In all of this, there is room for leniency even for religious people, regardless of secularism.
Regarding the level of religiosity of the witness, he is supposed to be a Sabbath keeper. There is a place to qualify a witness who is not a Sabbath keeper these days, since nowadays this is an accepted norm and it does not mean that he is an unreliable witness (of course assuming that the problem with the Sabbath violator is his credibility). There are other reasons to qualify even if the problem is not credibility (for example, if the problem is to legitimize the offender, today there is an opinion that offenders are not a marginal minority but the majority of the public and it is not reasonable to allow them to be prime minister and president of the Supreme Court but cannot be a witness at a kiddushin). Indeed, there are some jurists who have qualified secular people today to testify. It is true that in the case of a kiddushin testimony, it is customary to be stricter, apparently because it is testimony to the existence of something and not testimony in a court of law that requires credibility. But I doubt whether there really should be a division, since a witness is required for a Sabbath keeper, and if he is a kosher witness for testimony in a court of law, there is no reason not to qualify him to perform anything at a kiddushin.