I dredged the link to the "Room of Duo" SCSI <-> PCMCIA Card Cage hack up from the Preipherals Links Project. Notice how conveniently the Ultra-Dock seems to be for mounting a PCMCIA Card Cage (like the one from the 1400) and this SCSI based version proves the point!

One has to wonder why/how Apple managed to derail the PCMCIA UltraDock after its announcement . . .