Cable then VDSL2

[dalu]

Hello,

ok following situation:
WAN via cable
From August 04 WAN via VDSL2, and WAN via cable is going away.
Now usually I'd just replace Cable with VDSL and be on my way.
But I won't be at home, and that's the tricky part.
I'll be in another country where I will have an internet connection.
But I'll have to access my home network and for that reason I have set up the openvpn server in pfsense and a dyndns entry.

Hardware PC Engines APU2C4.

So I was thinking to use bonding or bridging to combine igb0+igb1.
I'd connect Cable to igb0 and VDSL2 to igb1 and LAN would be igb2.

How do I do that and are there better ways?

So again,
Now: Cable -> igb0
From 04.08.2017: DSL -> igb1, Cable dead.
both igb0+1 should be 1 device or an alternative way to solve this.