A change of weight in a bridge will result in a change of tone. Brass bridge pins result in an increase of weight and other materials can make for a weight reduction. Different guitars will react differently to weight changes in the bridge.

Frank Ford, in his site at Frets.com has an article about changing the weight of a mandolin bridge;



In this instance reducing the bridge weight resulted in more volume. You will have to experiment with different materials and judge the results for yourself.