They may already have this so don't jump me for this. But how about for identifying yourself on another device, it only allows you to use the original account if permission is given from both ends. But say something unfortunate happens like your first device breaks or gets lost and you want a transfer, you email Classic staff like normal. Then from there they can just merge accounts checking with both account emails. This way it'd prevent illegal merging of stats and gralats and say your friend is on your account for some reason (which is probably a stupid thing in the first place) it won't merge stats, only allow the, to use your account. Which can still cause a great deal of damage still, but now you don't necessarily lose everything and they don't get everything you own now. Again, that may already be out there so I'm not even sure if this paragraph was necessary lol.