The issue I have with this notion isn't the unconventionality of the relationship, but with the implication that a wife's role should be that of a homemaker and nothing else
By all means have open relationships/marriages, each to their own and all that - but the suggestion that having a wife means her only role is to cook, clean and provide emotional (and possibly financial) support to the man while he goes off and is sexually gratified elsewhere is actually quite sexist.
What about a woman having a husband for the family's financial stability and her getting off with some other blokes?