hmmmm....
I dunno... I'm no theologian or church historian or anything, but it seems to me that the last thing that Paul would have wanted was to make goyim-christians be more like Jews. He even warned against others who were trying to do this very thing...he called them "Judaizers", these were Christians of Jewish heritage who thought that ALL new christians must FIRST be Jewish, be kosher, and Paul taught that (Paraphrased) "There is no Jew nor Greek, Bond nor free....etc....for all are one in Christ Jesus...", and he emphasized Grace and Faith over the need for observance of the law.
SO...I don't think that Paul, in writing this metaphor, would have been trying to coax goyim-christians to be more "kosher".
Just me thinkin...
Your Brother
John