There is no "healthy diet" that is universally applicable. Go back and look at the list of different possible restrictions in the parent post.
Then add the fact that many people are allergic to all kinds of different things.
Then add to that the fact that people of different ethnic backgrounds are adapted to do better with different balances of nutrients.
Any "hypothetical person" such as you describe would, fundamentally and inevitably, "normalize" one specific type of person and "other" everyone else. Claiming that "this is a healthy diet" in such a way would be grossly irresponsible, even if you then went on to list the features of a person it is "healthy" for.
Finally, even if you wanted to make such a description, the whole point of this thread is that we do not have a scientifically-rigorous-enough idea of what it would be to be able to do so with a high degree of certainty, even for a clearly-defined set of parameters for who would be eating it.
Because if we can’t answer this much much simpler problem then we have no hope of giving nutritional advice to a population that is as varied as you describe.
Plus different activity levels make different diets healthy - if you're a professional athlete needing 6,000+ calories per day, "healthy" for you is very different to healthy for me, who sits at their desk all day.
This isn't even accounting for personal preferences like being vegan, or religious restrictions.