Get down to bare motherboards, loose the weight and complexity of the power supply brick, power supply boards, disk drives, and cases.
Probably use 2 ATX style power supplies each driving 4 boards via a 1->4 octopus cable.
Only node0 has a disk drive, nodes1-7 boot via PXE from node0 and mount disk space over NFS from node0.
Maybe put a second drive in, probably in node0, with a cronjob that synchs the two drives. If the primary drive fails you could (in theory) just swap the connectors and reboot.
Don't run BCCD as the operating system image. Since we know Little-Fe's hardware we can do things with performance counters, video, etc. that the BCCD can't do since it has to be hardware agnostic. Little-Fe also supports software, e.g. PBS/Maui, which isn't appropriate for the BCCD. Maybe in the future those can be add-in packages via a Little-Fe list-packages repository. If this gets legs than we would want an operating system image that was more hardware agnostic so that people could take our plans and use the motherboards of their choice.