Of your starting list, one was signed, one wouldn't qualify for the international draft, and one was a trade.
Also keep in mind this will involve all of those 16 year olds that are signing, so now teams would have to choose between more sure things with lower superstar potential like Cespedes and Colas, versus guys who have the unlimited ceiling but are 5 to 7 years away from it. We already see that today in the MLB draft with teams choosing between college and HS players and how to weigh development versus potential.