[jasomill]

If every device is directly connected to every other one of n devices with Thunderbolt cables, each with its own dedicated set of PCIe lanes, you'd be limited to 1/n of the theoretical maximum bandwidth between any two devices.

What you really want is for every device to be connected through a massive PCIe switch that allows PCIe lanes to be connected arbitrarily, so, e.g., a pair of EPYCs could communicate over 96 lanes with 32 lanes free to connect to peripheral devices.