I've uploaded the preliminary schematic (EAGLE & PDF) and board file for Orthrus v3.0.

This version is the full deal. It's got an ATSAMS70N19 in the TQFP form factor and is set up for high-speed USB. The HSMCI interface is set up for A/B switching with the bus switch ICs, with both cards disconnected when card power is turned off. Since the S70 has a built-in TRNG, the entropy generator and its power supply are no longer present. The entire thing consists of the controller and its support systems, the two cards and the HSMCI multiplexer, the button, the three LEDs and the 3.3v buck converter to power the whole thing.

I'm going to see if I can get some ARM experts to chime in on the design and layout before I order it. I really want to get the hardware as close to perfect as I can the first time out. Assuming it doesn't spectacularly fail (and assuming I can get the firmware written in time), that version will be submitted to the judges for the Hackaday Prize. 

UPDATE:

After getting some design feedback (thank you very much, @cj), I've updated the v3.0 design. It's been uploaded, but since the files have the same name, I'm not sure Hackaday.io has it figured out. It may need time to update the caches or something.