MPTCP is a new(ish) protocol that is being implemented in several locations.
It allows load balancing/failover in a new way - a single TCP connection can use different paths throughout the connection. This means failovers to backup connections would occur without interruption to the TCP connection, and bandwidth could be shared across multiple WAN connections in an amazing new way.
Apple is already using it for their iPhone to allow using your WiFi network for talking, and then seamlessly transitioning your phone call to the wireless network when you go out of range of WiFi.
I think it would be an amazing feature for VyOs, and would put VyOs ahead of the competition:
It’s already implemented in custom Linux Kernels, so it should be fairly easily integrated into VyOs.