Well, as long as those chips aren't custom or PLA's on the mediator, I dont see any reason why one couldn't build a "single slot" version using the same chipset which has a connector (and passthrough) for the A1200 and a wide cable to connect to the PCI card which could then be stuffed in the case where a 3.5" HD would normally get stuffed.
That mediator looks pretty simple to me, but I have no idea what those IC's are since I don't own one

A nice high resolution front and back image of the card might help.
vic20owner