This thread is just speculation. I do not believe in replacement theology.
I do not believe in replacement theology.
Strange, because Dispensationalism embraces 'replacing' Jesus Christ and the Church with 1948 secular nation Israel. Dispies also "replace" Israel with themselves in passages like Jeremiah 29:11 when the passage is clearly about the captive Jews (see v 4). Or when they try to prove "Free Will" in passages like Joshua 24:15 by replacing Israel with themselves. The list is boundless of examples where modern Evangelical Dispensationalists routinely replace the proper focus of the passages with entirely inappropriate characters - most egregious is in Daniel 9:26-27 where our LORD is gratuitously replaced by the Dispensationalists with a purely invented "antichrist" character. So you folks own "replacement theology".
As for us commonly insulted 'Realized Millennialists', the Gentiles don't "replace" "those of like faith of Abraham" (Gal 3:7-9) rather, "expand" it. Remember, in Hebrews 11, Abel, Enoch, Noah, Abraham, Issac and Jacob were not Jews under the Law of Moses yet are of the Church bound with thousands of years of Believers in faith. Dispies can't explain that in their artificial bifurcation of the Church.
Getting to the subject matter of your speculation, you are hurling elephants with the forced interpretations that try to make the round peg of Dispensationalism fit in the square hole of Grace/Faith. Approaching something a priori is not a good hermeneutic - its technically propaganda.
First off, the parable is only told in Luke - a Gentile gospel. Usually when one runs into things that should interest most the Jews, it would be in Matthew.
You are also deliberately ignoring the context of the occasion where our LORD presents this Parable. in the first verse of chapter 15 we see that the Scribes and the Pharisees were bitter about our LORD "receiving sinners". It would be inappropriate and wildly out of context for Jesus to then get into a discussion of dividing the people of faith between Jews and Gentiles particularly since our LORD did not minister to Gentiles (Matt 10:5-6; 15:24) and His present company was exclusively Jews.
Our LORD justifies His ministry to "the sinners" using the parable of the lost sheep, then the lost coin to lead up to His condemnation of the Pharisees and Scribes in their contempt of our LORD "seeking the lost".
I think it is painfully obvious who the younger brother and the elder are. The elder is the one who "kept the Law", thought he lived a perfect life and was pleasing to his father - this clearly is the sentiment that the Pharisees and Scribes "knew" they had with God in their mastery and keeping of the Law (in their terms). Being that in this context there are three actors, the father and the two sons, we can easily surmise who the Father is which leaves by default the "tax collectors and sinners" which is depicted as the younger.
On completion of that segue Parable, our LORD now strikes to the heart of the problem of the Pharisees in the Parable of the Unjust Steward. They clearly saw themselves there (16:14) and were now insulting Jesus because he revealed the bitter sinners that they are.
Taking the entire scene as a whole, it is a brilliant reprimand and condemnation of men who thought that they were better than the "tax collectors and sinners". He takes their own objections to who they are, and turns their accusations against their own hypocrisy revealing who was most in need of the Savior.
This is a common problem with Dispies. Isolating select passages of Scripture from the greater context and then applying an interpretational template that in effect creates a circular argument. I suppose there might be some vain satisfaction in trying to defend the undefendable, but in the process you miss the Glory of God.
Commentaries can be your friend. Christianity has been around for millennia and the Prodigal Son is one of the most commented parables. Do you really think that after all these centuries you would be the only one who has the Truth?
Guard rails, friend.