It has to be suited for human consumption too though.

I wonder if this has any real benefits over just doing very simple html wireframing with highly constrained css, which is readily renderable for human consumption. I guess pure text makes it easier to ignore many stylistic factors as they are harder to represent if not impossible. But I'm sure that LLMs have a lot more training data on html/css, and I'd expect them to easily follow instructions to produce html/css for a mockup/wireframe.