Wan fail over with 1 public IP

Hello, i’m working for local ISP and we have client that wants to make wan failover but he need to keep his ip adress. We got fiber and radio installed already. Is there a chance i can make it work? We are using pppoe to identify and also i tried doing it with 2 pppoe clients (with one credentials) . It partially worked, bcs internet was going down for about 4 pings after i disconnected one of the port. The problem is that it isn’t going back to fiber.

I think i found a solution, using bring with one pppoe client and diferent prio on ports in it. Is it good or is there better solution?