I have such a setup - the local connections at the end-user sites are inexpensive consumer-grade connections (because they are cheaper and quicker to set up than a proper leased-line which has months of lead time, and you're not going to convince small restaurants/coffee shops that they need to spend 500 bucks/month for a leased line to serve public Wi-Fi) with various bullshit such as filtering, dynamic IP, etc - but the network hardware tunnels back to my infrastructure and abstracts away all the intermediary connections, giving them a "clean" Ethernet port. As a bonus, it can tolerate intermediary connections failing without dropping in-flight TCP connections, since those run over the tunnel rather than the raw interfaces which have gone down.