Is the idea of a Redeemer something Paul invented?
The idea of a Redeemer was not invented by Paul; it is not Pauline. From Adam's sin onward, God prepared for the coming Redeemer, and Old Testament writers like Job and Isaiah looked forward to Him. Paul simply puts the cap or frosting on that existing truth.
Les teaches that the whole concept of a Redeemer is not Pauline. He uses the story of a little boy who made a boat, lost it, and then bought it back, saying, 'Little boat, I made you. I lost you. But I have bought you back. You're mine.' Les explains this is exactly what God did: God lost us when Adam sinned, and for 2,000 years He prepared for the coming of the Redeemer. Old Testament saints like Job looked forward to the Redeemer. In Isaiah 59:20, there is prophecy of this coming Redeemer. Les says Paul puts the cap on it and the frosting on the cake, but the concept existed long before Paul, and then he directs attention to Romans chapter 3.