Yes - I agree with your main points & I do think our church forgets that this is the purpose to the Apostles, not priesthood, but linkage and fulfillment of OT promises by Christ.  The twelve original Apostles are necessary to fulfill the promise to Abraham that his line will be the nation & kingdom that shall never fail.  This requires that 12 representatives with proper lineage be chosen.  With these 12 Israelite blooded, or Abraham blood containing men, we have the symbol of the 12 bridges from the Law who have crossed over to become the 12 foundation stones of  Faith in the Messiah.  12 men who are people of the Atonement and Salvation - they are both Abraham and Jesus Christ in the flesh and soul & spirit.  This makes the Church also the continuation of Abraham's person as God promised, not just the continuation of Jesus' person.  In the end, Jesus Christ is the judge of all (Jew or Gentile) that have been saved thru faith in his name & no apostle would judge against Jesus' will.