This study develops a dual-model theoretical framework for Dedollarization in the expanded BRICS+11 coalition. The first model formalizes currency adoption with network externalities and a geopolitical shock, showing that a sufficiently large shock can tip the system from a stable dollar equilibrium to a BRICS currency equilibrium. The second model analyzes strategic coordination among heterogeneous member states, deriving conditions for a grand coalition as a Nash equilibrium. Linking the two models through coalition size and switching costs yields four testable propositions: Dedollarization requires joint satisfaction of tipping and coordination conditions; pre-emptive infrastructure investment lowers the required shock; member heterogeneity can prevent full coordination; and a lead country with credible commitment stabilizes the grand coalition. The paper concludes by outlining policy implications and promising empirical strategies, while acknowledging that the framework's testable propositions require careful operationalization of geopolitical shocks and coalition heterogeneity.