What is their mental health condition like? How would the average person on earth cope with the extreme conditions they might face on Mars? How many of the current crop of Gen-Z even have a chance to be considered - even if they have technical skills?

I heard a podcast with a former astronaut, and he was explaining why he wouldn't go to Mars just because of what you cited. Mental health will be a difficult challenge to face the extreme conditions of the planet. The planet suffers with extreme radiation and weather. He mentioned that the first group of humans there would give a nice reality show with one fighting with the other and with big fights.

People need to remember that a trip to Mars even talking about 20 years will be a trip without return. It will be comparable with the first Europeans in the Americas, arriving to a new land without structure, but with terrible environmental conditions.