TLIK: If Yirei Shamayim want to completely conform to halacha, they absolutely can do so. We both know how halacha has extremely harsh words and condemnations for those that utilize arkaos, to the point that even if both parties agree to use a secular court instead of Beis Din, it is strictly forbidden. And that it is even forbidden for both parties to agree that Beis Din can utilize non-Jewish laws in their decision rather than straightly follow halacha. Even if both parties agree and would be happy to accept such an arrangement.
In many cases (depending on the state of residence and other factors) the parties could simply not file any court case or otherwise involve the courts. They could separate and mutually agree on the issues without a court order. Even if that isn’t feasible, they could involve the court to the minimal extent possible. Even in New York, they can file an “Uncontested Divorce” agreeing to their own terms for property division and child custody. While you’re correct that NY has legal the Child Support Standards Act, the spouses are legally able to jointly file a “Stipulation Regarding Child Support” that opts out of the state Child Support Guidelines and sets themselves the terms and conditions of the child support.
L’maaisa, there’s no halachic basis to force one spouse to give unfettered unaccountable funds to the other spouse in the name of child support, that many have pointed out is often inappropriately used for other purposes. His obligations to support his children can be met by him directly expending the funds on their behalf without necessarily involving his ex.
Regarding property division, it is well known that halachicly almost all marital assets belong to the husband. There is no reason, rhyme or basis to deviate from halacha in order to achieve the secular non-Jewish ideal of something like a 50/50 split, that has no halachic basis.