Retrofitting a Double Edge system into a JEM would be costly
(purchase of the JEM, purchase of DE-equipped guitar, installation, etc.), take a ton of time, and kill any hopes of retaining resale value.
...but, I do know one guy who put a DE-system in his DNA. :-)
A better option: purchase an RG-2020X or the RG-2120X and route out a
Monkey Grip and the Lions Claw
(click on the Universal Jem's banner above and ask them for a quote). Re-finish if desired, but be VERY CAREFUL of the trem. The wires and components "underneath" the trem aren't made to be handled excessively.
Good luck!