The libertarian dream of marriage privatization has mostly already come to pass
Libertarians talk about getting the government out of marriage, but it seems to me, for the most part that has already happened. There really aren't any major benefits to getting married, other than the spousal/fiancee visa. Most of the benefits are just piddly stuff, like getting a few days off work for bereavement leave if your spouse passes away. People talk about presumption of paternity, but when I was in family court, they didn't even take seriously that I was likely the child's father until I got a paternity test.
So basically, the libertarian brave new world of marriage being just a private contract, has already come to pass. Especially with more and more people just opting out of marriage and doing without any contract at all, because they figure, "How am I going to enforce this anyway" or "Why would I need to enforce this". Contract or no contract, the husband is normally going to keep supporting the mother of his kid, as long as she stays faithful to him; while looking for whatever other sexual opportunities he can have. Contract or no contract, when the husband stops bringing home the bacon, the wife is generally going to look for some other man to sell her pussy to, unless at that point she's just keeping the father of her kids around as a special kind of babysitter and as a man to fuck who's better-looking than the alternatives that she could attract on the market with her faded beauty.
The incentives are the same as they ever were; nothing has really changed, other than that illegitimate children now have the same benefits as legitimate children. Nobody frowns on fornication anymore, now that girls are going to college till age 25 and focusing on their careers till at least 30. A girl who went that many years without having sex, would be looked upon even by traditionalists as sexually repressed. Even the Catholics at this point have to acknowledge, the only viable option at this point is just to sin and then ask forgiveness, which of course is nothing new to them.
So topics that I bring up in my campaign, like marital rape, are not even all that big a deal. Regardless of what the law says, the husband is generally not going to be able or willing to rape his wife. Even if he's allowed to spank her, she can still be stubborn and refuse to submit. The only purpose of allowing such measures, is so that she can't use accusations of his having behaved in that way as a weapon against him in family court, after she tolerated that behavior for so long (and maybe even enjoyed it as a form of dominance, before he went beta).
Yeah, we can cut state funding for girls to attend college, but parents will still send their daughters there, and seek privately-funded scholarships, if the culture doesn't change.
What else is left? Oh yeah, allowing older men to bang and impregnate teenage girls, including their own daughters. (I kinda wonder how much that's already going on, by the way.) Well, radical libertarianism would tend to support allowing that. So basically the split between me and the Libertarian Party is mostly a radical vs. moderate libertarian thing. It's not necessarily even about patriarchy vs. feminism (although certainly it has that dimension to it, much as the drug war has a sexist and racist dimension), as much as paternalism vs. freedom.
The bottom line is, women will always have the same demands and expectations of men, regardless of whether the law commands patriarchy; and men will always have the same burdens. Sexual polarity of dominance and submission will still need to exist in order for there to be attraction. Strong men will continue to get pussy, and weak men will continue to get screwed over by women, regardless of what the law says.