It solves nothing actually, it would only mean cramming more people into the same area. So the consumption of resources don't change, potentially increases because most are very wasteful.
But, NO ONE would voluntarily do this. We suffer from a god complex as is, so there would be people that refused to take part so they could be the giants in a miniature world and rule over it. Not to mention it would put us in threatening position to even small predators and we could overcome most of it with knowledge, but no one would voluntarily make themselves more vulnerable. God complex, remember?