I agree with the OP that people assume monogamy as the default is an interesting relic. I often speak to atheists that hold many distinctly Christian notions without realizing it and having no real justification for them.

I may get downvoted for what I am about to say, but feel the need to disclose since I wish to check for faults in my reasoning as well as any ethical objections (I request you thoroughly explain the reasoning behind such objections from first principles up).

If I only want safe sexual pleasure I am better off financially seeking professional services.

If I want companionship in itself I have many friends both male and female which provide similar psychological benefits.

Bonding can make such exchanges more stable and long lasting, but considering the high divorce rate and turnover rate we see in modern socioeconomic conditions this is probably not something to depend on.

The only reason evolutionary speaking to bond with someone is to increase the odds of our genes spreading.

There is no such thing as a special someone. I could live relatively happy lives with a non trivial fraction of the population either in monogamous or alternative arrangements.

Romantic love is a just a special state of mind not so different from being high on any sort of drug. I shall therefore plan in advance on how to reduce or increase the likleyhood of faling in love so it matches my long term plans. Any drug I take must help me reach my goals according to my values, I despise hedonism.

Repeatedly having sex with the same person increases the likelihood of bonding to them.

Rates of false paternity are overestimated by most popular science claims and urban myths but still a factor to consider (3%).

Psychological differences between men and women. Women are hypergamus. And women on average prefer to be dominated rather than to dominate someone they are sexually attracted to.

For all the above statements I can provide citations and elaborated reasoning on request. I may ask for some patience since I still have a few crucial exams in the upcoming week but I will provide them after this period.

Before proceeding let me first point out I don't consider happiness in itself to be a goal for me. Happiness in some quantity is simply a necessary condition of following my goals optimally.

I have decided that I shall avoid sexual relationships unless I have judged the girl in question to have a sufficiently high IQ and reasonably attractive. One nights stands are an exception to this rule, after analysis I've concluded they feature in like a free prostitute service, so they are accepted when needed but I strictly close of further contact to avoid increasing the odds of paribonding.

I have relationships only with women who I see as potentially good mothers and carrying good genes.

A wild oats strategy unfortunately isn't going to work since I need financial resources to pursue my other goals (living a thuggish baby daddy life may be evolutionary optimal in my country due to the welfare state but I may not have the genes or mems for it) and the state can force me to make payments for children I sire.

I make it clear I will not accept sexual intercourse on her part outside the relationship (any other GFs I have are theoretically part of the relationship but I've never heard any such desires expressed by them).

Also all children will be tested for paternity as policy in order to equalize both our risks (she knows she is the biological mother of her child by default, I without tests do not have that certainty)

I reserve the option to have sexual intercourse outside the relationship and more than one girlfriend/wife. I must however insure minimal risk to STDs and inform the wives/GFs before having sex outside the relationship.

These policies are by most Western standards selfish. However I do lay them bare before beginning the relationships. I see no reason to desist them as they serve me well and women who I date judge my value sufficient to accept them and are fully informed. If they do not consent I politely terminate contact trying to minimize any trauma they experience with the severing of any potential pair bonds or infatuations that may have developed in that short time.

I have not had many relationships since I've implemented this policy. Ironically my relationships have become more LTR and much closer in practice to the monogamous ideal.

In many ways my lifestyle choice and evo strategy is very very conservative and traditional after one reviews how polygamous societies function.