I really like the system he uses to access video RAM which is simple, decouples the video from the main RAM (which is a serious weakness of real 8-bit machines because it hurts non-video performance directly as well as limiting the clock speed) but is also high performance (if you are blasting out a block of data to the video you can just blast out the bytes to a memory mapped location and the address pointer counts up automatically.)
This was standard on the PC-Engine, and I think the majority of VDC type display controllers of the time.. Personally, I’d take a bank switching scheme whereby CPU reads come from RAM as standard and CPU writes go to graphics memory.. Even as simple as 1 bit mapping of writes to either CPU RAM or VDC RAM would suffice well.. Though more complex is possible..