"Spiritual body"

Some people think Paul's reference to a "spiritual body," denotes an immaterial body. A subjective vision. They therefore deny that Paul affirmed the physical resurrection of Jesus. 

But if a "spiritual body" is defined in contrast to a physical body, then a "spiritual body" is synonymous with or indistinguishable from a ghost? Assuming they exist, ghosts have a corporeal appearance. On that definition, Paul would be saying Jesus became a ghost three days after he died, and since Jesus is the template for the Christian afterlife, Corinthian Christians will become ghosts in the world to come. 

But that's a highly implausible interpretation of Paul's argument in 1 Cor 15. Given widespread belief in ghosts in the ancient world, there'd be nothing special about saying Christ or Christians are immortal in that sense. 

If, moreover, "resurrection" is synonymous with ghosts, why would there be any chronological gap between death and becoming a ghost? Wouldn't that happen when the soul separates from body, at the moment of death?