The minimum viable demo for Capability Based Security

I have a vision of how computers can be made secure, but apparently in order to convince my fellow programmers that it can be done, it is necessary for be to build an "existence proof". Clearly I'm not up to building an Operating System, not even a custom linux distro.... something far less ambitions is required, a minimum viable demo... I'll be pondering this for a while, any suggestions would be appreciated.