Matt,
You're right, the generality that inertia changes gamma is not true for a teetering rotor, but the stresses that the rotor sees when "forced" to flap out of sequence by the rigid connection to the other blade is a factor.
Every pound of blade weight is probably a lost 2 pounds of payload, since the blade's inertia puts large stresses on the head, the mast and the transmission case and feet.
Some inertia is needed, too much is very costly to the rest of the design.