I’m not sure how many ports are needed, though I’m sure more couldn’t hurt. This seems less about expansion externally than doing so internally. My MBP with 4 USB-C ports has one that is power + hub (HengeDock Stone) with one of the USB-A ports on it chaining to a USB-A (powered) hub. One other port is used for eGPU and the other two are untouched. Works for me, but I can completely see where this Mac Pro could end up needing a hub attachment for a lot of people.