Q. The question I have is this ; “What is the Purpose of the Church Age when Gentiles will also be saved in the Tribulation ?”
A. 1 Peter 1:10-12 tells us neither the prophets of old nor even the angels in heaven really understood what God was going to accomplish through the Church. But Paul revealed it to us.
He said God raised us up with Christ and seated us with Him in the heavenly realms in order that in the coming ages He might show the incomparable riches of His Grace (Ephes 2:6-7). Then in Ephesians 3:10-11 he said God’s intent in doing this was that now, through the Church, the manifold wisdom of God should be made known to the rulers and authorities in the heavenly realms (angels) according to His eternal purpose which He accomplished in Christ Jesus our Lord.
Put these two statements together and you can see that God’s purpose was to demonstrate the full extent of His capacity for love, and He chose to do so through the Church. When we were dead in our sins He made us alive with Christ. He forgave us all our sins and canceled the list of our violations of His law (Colossians 2:13-14) and now regards us as a new creation, as righteous as He is (2 Cor. 5:17, 21). He gave us the authority to become His own children (John 1:12-13) and made us His heirs as well (Galatians 4:4-7). He raised his Son from the dead to a place at His right hand with authority that far exceeded any heavenly power (Ephesians 1:20-21), and then He raised us up and seated us there with Him (Ephesians 2:6-7).
At the appointed time He will send His Son to collect us and take us to a place of unimaginable beauty that He has been preparing for us for almost 2,000 years (John 14:2-3). In doing so He will rescue us from the time and place of the coming wrath (1 Thes. 1:10, Romans 5:9) and we will dwell with Him forever (1 Thes. 4:16-17). We won’t have done anything to deserve this, except to believe that He did it for us.
I think that qualifies as an unparalleled demonstration of the incomparable riches of His grace.