Sorry to dig up an old thread, but I just picked up a '64 Epiphone ElDorado (at a too good to pass up price) that has the plastic bridge and ceramic saddle. Unfortunately, the bridge is cracked on the bass side and is pulling away from the top, so replacement probably is the only option.I didn't look at the bridge plate with a mirror, but it feels like it's cracked, so it'll probably need to go also. I strung it up with .11s and it sounds good with good intonation, but don't want to do any further damage.
I left for a short vacation right after I got it, but will pay a visit to my local luthier next week to see what he thinks. The guitar is in good structural condition other than the bridge, but cosmetics are not up to collector standards, so I'm probably not hurting any "originality" by fixing a broken part.