Re: Sharingan Swapping Issue
ok, I searched through the manga, and can't find a single instance or suggestions, or implication, that the eyes fuse.
What I did find was sasuke with a bandage over his eyes, as though he had just had new eyes implanted.
What makes as much sense is that the eyes, infused with new chakra, are rejuvinated. Operating under the Nietzsche philosophy of "what doesn't kill you, makes you stronger" they eyes repair to be even more powerful than before.
Problem is, if this is the case, then anyone could get EMS by taking a MS and transplanting them into themself. Of course, it's not said that one must be an uchiha to get EMS.