I know this will come up at some point, as one of my players is pretty keen on getting a silver lightsaber, which apparently is a sign of redemption or something. After thinking about it a bit, I think I like the option to be there anyway, and I want to come up with some kind of mechanical framework. I'm thinking there are three different circumstances under which someone would reattune a crystal:
1: Taken from an enemy and hoping to purify/corrupt the crystal while the owner is still alive. This is what one of my players has already asked about. I'm planning on making it work, but not how he's thinking. Should be the hardest, in my opinion, as the original owner is still tied to it.
2: The owner is already dead, either because you killed him, or you just found his saber. Attuning it to yourself would allow you to modify it at the lower difficulty.
3: It's your saber anyway, and you're doing a "reforge." I'm thinking that reattuning should wipe the crystal clean of mods. This would help folks who are attached to their first lightsaber, but who botched some early rolls. They need to spend some more credits and make some new rolls, but hopefully they've beefed up their stats since they blew it.
My first thought is that the base difficulty should be equal to the current difficulty to install a new mod. Maybe it would cost the same. So if you're reattuning your own, it won't be as hard.
If the owner is still alive, you upgrade the difficulty once per each point of his Force Rating (or maybe for every 2 points). So purifying the crystal of a Sith Lord is going to be real tough, and a Despair will carry some nasty consequences.
So that's my 12:45 am brainstorm. Whaddya think?