I hear a lot of ideas, which ignore the indications from both China and South Korea about re-infection. Nobody for sure knows how long the immunity lasts. Also, people could be asymptomatic/mild-symptom, just because they have a strong immune response, not because the strain is less deadly. How do you quantify who is immunosuppressed and who has a well-functioning immune system?
I read your idea, but it doesn't address the exact points I listed - selecting a "less deadly" strain and having fingers crossed that immunity persists. So far, many have insufficient antibody counts and get reinfected. I just saw a number around 20%.