My ideal partner would be a domme who is also a romantic companion. By romance I refer to things emotional versus things sexual.
If I had to choose, I am more likely to go for romantic companion who is not actively into dominance (but is open to it) than a woman who enjoys dominance but there is not enough interpersonal or romantic compatibility. I think a relationship has greatest long-term promise if it satisfies wants for companionship (romantic or friendly companion), or brings spiritual fulfillment. I am less optimistic about a relationship that brings sexual gratification only. The more time spent together, the more I see this idea to apply.
For me, interpersonal compatibility supercedes D/s compatibility. While my ideal relationship would be a romantic companionship with a domme, I recognize other possibilities: a relationship with a vanilla woman who is open enough to BDSM (some aspects of submission align well with romance and love), an open relationship with a vanilla woman, or to be a part of a sub-sub couple.
The context of my statements above is a long-term relationship that spans life in general. For a relationship that is based on D/s alone, an ideal partner would be one with whom there exists chemistry. attraction and trust as well as reasonable compatibility of D/s interests.
Cheers,
Sea