Balance 20 drop in mode

There is this deployment I want to set up in a client’s home. He has two ISP routers from MTN and VODAFONE as shown in the diagram. He has a Mikrotik router which has VPN services configured to allow him to watch some TV Services over the internet. The problem is he uses one ISP at a time which works for him but one ISP is mostly unused (idle) till the main one is off before the backup link is plugged into the Mikrotik manually.

We are trying to introduce peplink Balance 20 into the network so that he can enjoy hot failover and speed bonding. The challenge here is when we introduce balance 20 into the network he is not able to have access to his TV services. I want to configure the balance 20 so that the MikroTik firewall will not be touch yet able to watch his TV series. I have seen a drop mode configuration but only public IP been used other than private IP as in the case of my client.

Can someone help with the configuration steps?