A copy is never good enough. I think the best approach would be to enhance the brain by attaching devices to it directly. This maintains continuity and doesn't raise as many philosophical questions. This also raises other interesting questions like how long can the brain live in a suspended solution and where would all these consciousnesses live...
Slowly replace organics with mechanics until you only have a machine left. If you keep it gradual, you never know when you stop being a cyborg and start being a full fledged android.
