I think I've read this idea a few times, possible from yourself, but a sheathe that can catch and store the expended energy would be a good idea. As its been mentioned, a saber that comes incontact expends energy. But as it gives off heat, that heat might be able to restore what is loss. Perhaps a series of conductive wires or internal frame to catch and transport the energy back to the weapon could be a good idea.
[member="Edgy Wind Jedi"]
(Edit: as mentioned before, phrk, beskar, and songsteel are your best bet. Unless you want rapid transfer of energy to storing device, then perhaps ultrachrome with some sort of cooling system incase it overheats would be a good idea)
Also, for people telling him to just drop the idea... its an interesting one. Maybe not the most practical, but the emporer spent billions of credits to build a giant moon station... slave driving and hyperspacing a much less costly ship would have been faster and cheaper. Stop trying to discourage a possibly interesting character idea simply because 'its not what I would do,' when he's trying to find a reason behind said idea.