Yes, I think that should be allowed, but only with binding effect for the employees in the union, not the others. Certain protected concerted activities are al

Yes, I think that should be allowed, but only with binding effect for the employees in the union, not the others. Certain protected concerted activities are already allowed with even 2 out of 50 employees. E.g. a a man could legally go to his employer saying "please fix [my female colleague]'s salary to be more in line with what you're paying me, since she's performing comparably. I feel strongly about this and might not stay here if this gap persists." The employer may value his services more than hers due to sexism or personal relationships, so this could help - and is NLRA-protected even without a union, assuming neither is a supervisor and both are in the US private sector.