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

Can you go into more detail about your Bell Fibe TV setup? Does it only work in a browser or did you find a way to make it work with an Arris box or Android TV device (which, if it's on the Bell network, should let you watch any channel you subscribe to)?

I'm wondering how IGMP snooping/multicast would work through the tunnel if I wanted to put a box elsewhere.

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?

Check if your ISP has an SMTP service. I use mine for alerting when stuff breaks and haven't had any issues. If you use your own domain name and have trouble with delivery, you could try setting up SPF.