[nickpsecurity]

You'll get patent suits for sure if you sell it. There's a patent on almost everything about making CPU's and networked devices. Also, anything that uses high-assurance security (EAL6/7) is still under old classification they used to reduce exports for crypto. They didn't mention the implications of that when they opened up crypto exports. ;)

So, your best case is to build something that barely functions by modern standards but still usable. Here's you some inspiration:

http://www.homebrewcpu.com/

Good security model to start with to leverage existing code:

https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/