I've been very busy as of late...
Using your given example, what exactly are the benefits to this "higher" institution? And how would it benefit me, and why would I choose it? Speaking as a divorced person, being required to forfeit all of my "mutually owned funds" (including the house which I now solely inhabit) upon divorce doesn't sound palatable.
You're arguing a logical approach to a convenant - in effect arguing what are the benefits to be gained versus the risks being taken. (That's a good thing.)
Marriage is often entered into without this planning. In fact, there is the argument that marriage is entered into lightly because divorce is made 'simple'. (It's not simple, it never is, but that argument is sometimes made.)
The benefit would be threefold : first the use of the name of the covenant (being able to claim that you are in said covenant) and the (hopefully) increased awareness of the significance of the convenant and (again hopefully) the decrease in divorces (or breaking of the covenant) as more people would be aware of what they are getting into and the cost of getting out of it.
I have a friend who has been with the same woman for 25 years. They've been married for 19. 3 kids together. And she's just revealed that it's been a "marriage of convenience" for her. Oh, and that it's no longer convenient. So he should be forced to give away everything he's worked for over the last quarter-century? How will that help his kids, and keep them off the streets of South-Side Chicago?
Short answer, it won't. (I didn't claim it was perfect).
But, it would also prevent her from getting anything. It may give pause before the next couple thinks of "tying the knot."
The financials that I suggested were just one possibility. Another might dictate counseling for both parties before entering the convenant. (However, I have no statistics that suggest that would make the arrangement more palatable to the parties in 25 years.)
In short, I have no magic pill that will keep people together. Personally, I believe it morally wrong to try to keep people together when they (actually even if just one of them) don't want to be together. This will not prevent divorce.
My sole argument for Gays and Lesbians to take the higher moral ground, and in doing so, could surplant both criticism for their convenants and may even attact others to them.