@falken I will send you a PCB FOC if you cover postage (I've never made it into a kit. ), other than that you only need a handful of usb connectors, there is a hub built into the base pcb, but I'd suggest using it only to power the pico's due to multiple USB issues on most common OS's.
9 Pi pico's(1's) a display ~£7, a hand full of buttons.