In a now published paper in Games, Jonathan Newton gives a fixed point solution concept that incorporates collective agency under incomplete information.
In keeping with the ethos of the SI project, agency may be exercised by different entities (e.g. individuals, firms, households). A given individual can form part of multiple agents (e.g. he may belong to a firm and a household).
However, the set of agents that act in a given situation might not be common knowledge. For example, Alice may not know whether Bob and Colm have formed a coalition and constitute a collective agent.
The paper models such considerations, inspired by the classic model of incomplete information over preferences of Harsanyi.