You could convert an old army base into a temporary 'new town' - Loopyville or whatever you want to call it. Invite people to go live there free bed and board and free rein to just live and mix as much as they like. Let them sign a disclaimer for if they catch Covid and need to be taken out or to hospital but test them daily and study their movements with CCTV and aps. Give them all the facilities and a pub, sports fields, gym and a theatre etc etc to do what they choose.
Then see what happens.
At least then it is voluntary if they all get sick. And instructive to what really does drive infections.
Not being serious of course but it would be a very interesting experiment.