Tandemplex

Tandemplex:

A tandemplex is a system with no 'main' subsystem or sidesystem. A tandemplex instead has two or more sub/sidesystems that feel roughly equal to each other in population, rank, headspace size, etc.

A tandemplex can have smaller sidesystems or subsystems, the only prerequisite for using this label is that they don't have a single main subsystem or sidesystem, and instead have more than one that serve that function.

Etymology
A tandemplex is named after a tandem bicycle, two riders who both have an equal role in pedalling.