(for example, he takes care of their kids while she goes to school)

How are they making a living?

I think if two people are in a relationship where one person is making all the income, they, together have a responsibility to figure out beforehand how they will plan for the relationship ending. I think in today's world its clear few marriages till death. So both people in the relationship have a responsibility to plan for what they are going to do when it ends.

then he should just be content earning minimum wage while his ex wife lives lavishly with their children?

Isn't the flip side kind of bad too? Should just Husband just be able to ditch the Wife, leave the kids with her, while the Wife has to support the husband too? What if the Husband is content to live off what the wife sends him? What if he moves to like, Indonesia or somewhere the dollar has large buying power. Spending his days on the beach hitting on women and drinking coconuts, while his Doctor Wife works, takes care of the kids, and cuts him a check every month?

I mean, you can make all sorts of cases where either side could be "right" or "wrong". Which is why blanket rules don't work. But blanket rules is pretty much all that is going to happen if the government is involved.

I think instead people should just be more responsible. If your in a relationship where the income is heavily lopsided, and the other person is taking care of that children.

1. The lower income person should be able to save proportionally more of his or her $, or even have savings invested in by the higher income person.
2. The lower income person should be spending the 6hr/day the kids are in school productively.

You could literally work a minimum wage job for those 6 hours a day and have like, two hundred thousand dollars if you get divorced after 20 years.

If you leave a relationship and your more or less destitute I have little sympathy for you baring special circumstances.