plebs, priests and unbelieving partners

I'm currently reading through Leithart's thesis, 'The Priesthood of The Plebs' which seeks to demonstrate how Christian baptism initiates priesthood so that baptism should be seen as the fulfillment of Aaronic ordination. Chapter 1, which Leithart notes in his preface, contains 'vignettes from the history of sacramental theology ..(that are) far to compressed to make much sense to anyone unfamiliar with the debates' [I definitely fall into this group] is excellent in stating the case for where he thinks Reformed and modern sacramental theology has gone wrong. His contention, following Augustine, is that The New is a ‘conjugation’ of the Old and therefore a ‘treatise on the sacraments of the Old Law must serve as prolegomena to a treatise on the sacraments in general’, something much of post medieval Christian tradition has singly failed to do.

By the time he gets to Chapter 4. Leithart applies his findings from the previous chapters to infant baptism. In seeking to demonstrate how infants contribute positively as members of the Christian priesthood and should therefore be baptised, Leithart quotes Mark Searle

a newborn infant alters the configuration of family relationships from the day of its birth, if not sooner, having a major impact on the lives of its parents and siblings. . . . Children will test the sacrificial self-commitment, the self-delusions, and the spurious faith of those with whom they come in contact for any length of time. They summon parents particularly to a deeper understanding of the mystery of grace and of the limitations of human abilities. . . . All this is merely to suggest that in their own way children in fact play an extremely active, even prophetic, role in the household of faith. The obstacle lies not in the child but in the faithlessness of the adult believers (153).

But, on the basis of 1 Cor. 7:14, to which Leithart alludes to suggest infants of believers are holy, shouldn't there be an analogous requirement for unbelieving husbands, whom Paul also identifies as holy, to also be considered as those contributing positively as members of the Christian priesthood.

an unbelieving husband alters the configuration of family relationships from the day of the spouses conversion, if not sooner, having a major impact on the lives of the believing spouse and any children they have. . . . The unbelieving husband will test the sacrificial self-commitment, the self-delusions, and the spurious faith of those with whom they come in contact for any length of time. They summon the believing spouse particularly to a deeper understanding of the mystery of grace and of the limitations of human abilities. . . . All this is merely to suggest that in their own way unbelieving husbands in fact play an extremely active, even prophetic, role in the household of faith. The obstacle lies not in the unbelieving husband but in the faithlessness of the adult believers.

I don't know any paedobaptist's who would want to affirm the above for unbelieving husbands, so why use this method of reasoning for the analogous case of infants?