The last guy that tried to tell me my warranty was expired got his space ship boarded and got flushed out of an airlock.

Now I get it. Could you unconditionally forward incoming calls on those SIMs to a voip DID and then sign into that service from abroad? You’d eliminate a lot of complexity and points of failure this way - your home setup is completely out of the loop.

I don’t really understand what you’re trying to do. Is the LTE gateway for home or for travelling? Why does it need to support voice - just use voip?