Okay, interesting point. But Christ in the parable then is sacrificed to feast upon, and not as an offering for sin. The identity is clearly not exact, which is why it is a parable. It is also why the parable speaks of the son only injuring himself through his folly, and not his offending his father.
The parable of the prodigal son is only incidentally about the forgiveness of sin. what it's really about is the extension of salvation to the gentiles. The tipoff is the presence of brothers. Any biblical story of brothers needs to be carefully read as a prophetic account of the way God has chosen to be merciful not only to the Jews but to the world at large. The parable is bursting with hints at this reading: the "younger brother" is the one who departs for the life of a wastrel. His honoring at the end of the story is an overturning of conventional expectations. He is said to have been dead, but now is returned to life. His degradation extended so far as to be making his home with unclean swine. The older brother is the one who's remained faithful to the Father, laboring in obedience. At the hour of his redemption, the younger brother "comes to himself" -- recovering his spiritual integrity.