I don't agree with the idea that paid sex is a better option than "full-blown polyamory." In particular paid sex is a lot of trouble and doesn't really resolve the issue that someone doesn't feel lovable or attractive.

In many cases of a sexless marriage it seems the non-responsive partner would be interested in dating anyone. (Though some women who seem asexual in married life might experience a sexual awakening if they found another partner; men seem to be satisfied with boring marital sex, women seem likely to lose interest and check out.)