I have seen examples of home-brew NAS units that use SAS expanders plugged into a host motherboard that has neither a CPU or memory, literally for the purpose of powering the card. If the card doesn't need the PCIe slot, why are they all designed to consume one? HighPoint make a SAS expander that uses a floppy frive power connector and the SCSI bracked mount, though I'm learning it is proprietary in the communication so unsultable for my needs.
Some example cards with internal/external ports. Interstingly the second card seems to have no pin contacts at all for the slot shape, how it is powered is ambiguous:
Would this board be effective at powering such cards? Would there be any missing features or functions?