I just received HLP-7688A module and looking at the size I must admit that I tempted to create a Switch/Router in Hat format. I am not os sure about the SPI on this, but it has 2 UART’s, so assuming I can control the code on the Linux module this could be interesting with Wifi and 3-5 10/100 Mbps Ethernet ports. The switch can manage 150Mbps so it is decent. Bandwidth to the backbone will be far less obviously, but it is an interesting idea.
The advantage compared to using Raspberry PI is (1) No SD Card boot, (2) multiple Ethernets and switch functionality and (3) Hat format. In fact I could support PoE out and use the WAN as another backbone to support larger switches. Just an idea.
I am still waiting on the dev-kits before I can play with this module.