Implementing a automated DB25 switch
There is a company that makes large-count switches and relays: T-Bar.  They make a nice 24-pole relay that would be perfect. Except that it costs US$761!  However there is a 48PDT relay currently on Ebay for $25 if you are fast enough to grab it:  http://www.ebay.com/itm/8447-T-Bar-Switch-Relay-8501-3023-43-94-ohms-24-VDC-FREE-Shipping-Conti-USA-/311310900801