Triads, or three way relationships, seem to be more common the more we discuss polyamory. However, the interpretation of what a Triad looks like varies greatly. People have visions of a traditional, monogamous relationship with three people all the way to a poly three way relationship where all involved do not necessarily live together.
What type of relationship works best depends on the people involved, but I believe the most important element is being open to creating what works for everyone. Regardless of the intentions people have going into the relationship, those intentions needs to be up to discussion and malleable. Envisioning and holding to just one concept of how the relationship can develop can be damaging to all involved and destroy something that otherwise could develop into something incredible.
All this to say I do not believe one should not have certain things they want to get out of the relationship. Of course everyone needs to make sure their needs are being met, but there are limitless possibilities as to how those needs are met. It is good to ask yourself why you need the things you do and get down to the root need which is below the surface.
It seems the most important elements of developing a triad are communication (not sure I can ever beat that dead horse enough) and making sure the “third” does not feel like the “third.” What I mean by the latter is making sure if there is an existing couple including a third in the relationship, that it is clear where the third stands. I believe it is most healthy to allow that person the ability to have a relationship with the couple up to the same level of relationship the couple currently enjoys. The only difference is the history of time spent together. Making sure the third is included at the level they wish is key as well. It helps them feel safe and recognized as part of the relationship. Excluding them from events, dinners, friend circles, etc. can be destructive if those are things the third wants to participate in.
The third can often feel vulnerable, particularly early on. They are approaching an existing relationship and often think they are disposable because if things do not work out with the triad, the existing couple will continue. This is unfortunate and can often be not far from the truth. Facts must be addressed, but one thing that seems to help is a lot of support for the third in the early stages. Frequent check ins (at least weekly) about where everyone is at in the relationship, where they see it going, their feelings, etc. will help.
Regardless of how things develop, realize it is something new to create. Most of this triad dynamic is uncharted territory. Instead of fearing the unknown, embrace the opportunities and create the relationship you all want.