pita, you are also discounting a variety of viable, loving relationships that go beyond, but can include the D/s relationship, whether online or in real life. There are many many people who are not monogamous (whether married or not,) who have wonderful closeness and love.

Polyamories, communal, and modern siraglios just to name a few.

I say, why not.

You eliminate possibilities if you close your mind to them.