Same case for me, purely hypothetical. I would be tickled if someone approached me with an interest in my husband! My husband and I have an agreement that he is able to pursue relationships as he feels comfortable. If he wants to have casual sex or date someone else, it's just a matter of communicating our expectations. My only concern remains that he maintains our relationship and that they aren't at the expense of our own. If he feels he has time for a wife, girlfriend, and someone else then I support his decisions.
He holds the same standard for myself, however I don't have the support of my bf for that kind of arrangement. He is mono and struggles with feelings of insecurity regarding any new relationship I might pursue. For the time being, I'm committed to my husband and boyfriend with no other relationships on the horizon.
"There are worse crimes than burning books. One of them is not reading them." - Ray Bradbury