I am really considering to do this, actually I have been thinking about this a few weeks now.
My ideas was not to create a CPU from scratch, but use 'a few' microcontroller, RAM chips and something like a STM32F4 to create a beast like a console.
Assets would be streamed from a SD card (SD cards can be easily used in SPI mode). Obviously that art would be needed to be downsized a lot. Output would be maybe around 640x480 or lower.
Obviously that would be a huge task itself. Also I am by new means claiming I am a hardware guy, it'll me more like me learning on the journey.
On of my biggest concern with this right now:
I have not idea what a footprint the final game will have. The idea be make the hardware and get Casey's code running on it. As both, hardware and rewrite the whole code would just be too much (IMO).