One can devise all manner of rules but they are not meaningful because the situation you describe is one of demobilization. A well-structured set of rules for an organization under such conditions makes no difference in terms of fostering mobilization. Organizations don't foster mobilization; they may be around to take advantage of it when it occurs, but in that case there would be no shortage of minorities to take leadership roles. I'd say the real issue is what rules should apply in a genuine upsurge, rather than at ebb tide.
I've started reading "Poor Peoples Movements" by Cloward and Piven, and they raise the -- for me -- intriguing question of whether "organization" in the usual sense is the real key to social change. C&P say that organization only happens as an upsurge recedes, and orgs tend to reconcile with the status quo in the aftermath. It's the disruption and potential threat that force the change. Where this takes us I couldn't say yet, since I haven't finished the book. But the reconciliation part of their story is persuasive.
mbs