Looks like it already has a Cree XP-x, probably XP-E or XP-G. Is the LED removeable? Assuming the back of the LED assembly is connected to metal, you could swap out the current LED for anything else that fits in there, like say an XP-G Neutral.
Does the back of the pill alos have a PCB? That one might be the driver and you might be able to swap that out as well. Both will be hard to do if the driver is potted and the LED is glued down.