That's an interesting idea. The closest thing I can think of is using an extended box-drawing font: https://hpjansson.org/blag/2024/01/18/chafa-1-14-all-singing....

That doesn't solve the two-colors-per-cell challenge. But it makes for some very realistic terminal images.

For higher fidelity rendering, I think the next best option is supporting image protocols like sixels or Kitty inline raster images. I'm not sure how overprinting would compare to existing options.