I have a 1964 Epiphone Texan (basically a J-50 with a sunburst top and Epiphone on the headstock) that had the adjustable ceramic saddle on a rosewood reverse belly bridge.
A local guitar repairman found me a bone saddle fitted with ebony shims that fits snugly down in the original slot. The conversion did change the tone of the guitar significantly. It became smoother and more rounded and gained a little volume, but lost that familiar growl that some of these 60's Gibsons have. Overall it's better to my ears. I've just been wondering what replacing the entire bridge and saddle might do for the sound. I'm tempted to try it, but i dunno.