I think Sayid is Jacob, no question.
I don't think Jacob took over Sayid's body and I hope that's not the case. It seems a little too obvious and kind of cheap.
I don't sayid was ever dead, so Jacob could never take his body. Miles knew something was up. His reaction indicated that he couldn't hear dead Sayid. Based on what we learned when Ben was healed, a person forgets everything prior. Sayid had a ton of baggage and now he is washed cleaned. I think there is double meaning when the Other said "your friend is beyond saving". It indicated that the Others thought Sayid's body and "soul" was beyond saving. It ties into a theme of the episode of what controls people. Locke told Bram they were free and Richard that he looked good without those chains. I think he was referring to them being "free" from serving Jacob. Obviously there is Locke manipulating Ben. Sayid was often controlled by his past and now maybe free. It is all variations on different things that influenced or controlled the characters' lives.







