How about an aluminum, kydex, or similar material clip on bracket which could hold the string ball ends securely in place in the "R" tailpiece while installing new strings. one could either clip it on the underside using one of several available contact points or use another means of attachment which could be as varied as the many different capo styles which come to mind. There would be no bridge modification, fit would be all but universal, and it could be offered in the online store. Just my $0.02;-)