Moshiah can come from the dead. (remember "dieng" isnt the end of a soul and life, and not even the body necessarily -ex- ressurection) But that doesnt mean I belive him to be Moshiah and frankly it doesnt matter at all who Moshiah is, but what matters is what can we do to bring the process of redemption, Mitzvot, Milhemet Mitzva, etc.
we shouldnt underestemate what Jewish scolars we have and expecially had. even the least mentioned person in the Talmud minimally was able to resurect the Dead. recently the Baba Sali did a number of miracles when needed for example hosted a large crowd of people during a celebration with only one bottle of wine. He kept pouring and pouring from the same bottle having enough for the large crowds that came to him. Another example was when he got into a Taxi in Israel, he needed to go somewhere and the meter said that their was little gas, he told the driver not to worry and the gas was enough for the whole long trip.