I don't agree with your manipulation of the text;
"
Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live"
Like when the physically alive but spiritually dead Pharisees were burying physically dead people and Jesus said, "
...let the dead bury their dead." (Matt 8:22, Luke 9:60). Death in the verse you referred to is a reference to a person who if (s)/he believes in Jesus, though (s)/he were (spiritually) dead, yet shall (s)/he live. Obviously people who are already physically dead can't change their beliefs if the JW assumption regarding people having no immortal soul were hypothetically assumed correct.
The whole context of the verse you quoted is regarding the already deceased brother of the lady Jesus is talking to. Furthermore it is followed by this verse 26;
"
And whosoever liveth and believeth in me shall never die." Obviously if Jesus was referring to physical death He would already have been proven wrong by the fact that the brother had been physically dead for some time.
Also, if Jesus were referring to physical death, this would prove beyond the faintest shadow of a doubt that not one single Jehovah's Witness member has ever been saved, since from the inception of the movement in the 19th century there has not been one single JW who
never died at all.
Kind regards