When it comes to finding synonyms for the phrase "need complementarity," there are a few options to choose from. One option is "requirement for interdependence," which refers to the need for individuals or components to rely on each other in order to function properly. Another synonym is "necessity for mutual support," which emphasizes the importance of individuals or entities working together to achieve a common goal. "Requisite balance" is another option, highlighting the idea that a harmonious interplay between different elements is necessary for success. Ultimately, these synonyms all point to the idea that complementarity and collaboration are essential for achieving goals and thriving in any given system.