"A lad is good friends with a woman who admitted she has a crush on him. He doesn't feel the same way about her..."

"...but knows she would make a great life partner. Should he suggest a companionate marriage from the get-go?"

The link goes to a podcast, and this part begins at 13:36. Unfortunately, there's no transcript. Also, the question-answerer is Dan Savage, and I already know some of you resist the charms of Dan Savage. Let's not get distracted by the difficulty of sitting through audio. (I recommend listening to podcasts when doing things — like putting on your makeup and making your coffee.) And let's not bother with the usual taking shots at Dan Savage. (We know about Dan Savage and the doorknobs, and I could lick a doorknob at night.) Let's get right onto the topic, which I will summarize for your convenience.

A heterosexual man and woman are true friends and get along great, and he's in his 30s and thinking he'd like someone to settle down and grow old with, but he has no sexual interest in her. He's had plenty of women sexually, but none of them are suitable life partners, and he doesn't think he'll ever meet another woman who'll feel like such a great wife. He thinks this woman might be up for any sort of proposal he'll make to her, so could/should he offer to marry her in a "companionate marriage," meaning he has no sexual interest in her and she should never expect to have sex with him, but he's committed to everything else about the life partnership?

You might want to know how much does she desire sex from him? Maybe there's some way he could first find out how interested in sex she is. Would a sex-free marriage in fact be a positive thing for her too? It seems unlikely, but that's a moving part in the analysis that he could try to pin down first. Also, would he give up sex for rest of his life? I think this particular man wanted to propose a marriage where he had freedom to seek out sex with other women, so the idea would be that she'd be agreeing to this arrangement, which would include his conducting these outside liaisons with discretion and respect and disease-prevention precautions. He'd grant her corresponding freedoms if that's what she wanted.

Note that this model for a marriage would enable gay people to marry someone of the opposite sex. It would also enable sexually unappealing persons to form life partnerships.

Savage's actual answer has a lot to do with the age of the man asking the question. He's in his 30s, but he contemplates the value of having this woman keeping him company when he's in his 80s and he imagines sex won't matter at all in half a century.

The term "companionate marriage" has been used to mean different things over the years. Searching the term in the NYT archive, I see that it was a big topic in the 1920s, and Bertrand Russell's name keeps coming up. Here's his 1928 article, "Is Companionate Marriage Moral?"

Russell defines the term to include a 3-fold legal aspect: 1. Recognition of unions in which the production of children will be avoided (at least at first) by using birth control, 2. Allowing divorce by mutual consent as long as there are no children, and 3. No alimony upon divorce where there are no children. The idea is obviously avoiding children, not avoiding sex.

In addition to the legal aspect, there is, Russell says, a "social" aspect. Conventionally, a married man and woman are expected to live together, with the man providing her economic support. But that's because children are supposed to arrive. If children are avoided, these expectations are not present, he says.

[T]here is no reason why the wife should not earn her living, and every reason why she should. There will be no interference with each other's work, none of the fuss and flummery which at present make marriage disgusting to young people of spirit, none of the foolish pretense of protection by the male and dependence on the part of the female. 

The moral topic here is whether a man without the means to start a family should be allowed to marry a woman so he can have sex. The "sexual instinct does not wait" until the man is economically ready to support a wife and children. Yes, a man could go to prostitutes, but:

Nowadays, young women, for the most part, no longer feel bound to abstain from extramarital intercourse, with the result that unmarried men can have decent relations with women with whom they have much in common mentally — relations not founded on a cash nexus, but upon mutual affection.

Companionate marriage, then, was a way for a young couple, sexually attracted to each other, to live together openly. This was recommended over the alternative, which was "surreptitious," and tended to be "frivolous, promiscuous, and unduly exciting."

But our "lad" in the Dan Savage question wasn't fretting about "unduly exciting" sex. He was talking about no sexual interest at all. And the "fuss and flummery" of marriage seemed not "disgusting" at all, but the best part, desirable without any sex at all.

But that's what the term "companionate marriage" has come to mean these days. These notions evolve, and no one seems to wonder anymore about how to deal with raging sexual passions. Today's problem is lack of passion or lack of passion for anyone you'd want to live with along with a desire for long-term, committed companionship.