I get that, but in practice people judge the potential of a player based to a large degree on how good they are already, and the closer a player is to that top level the better the chance is they're going to fulfil their potential. There's a reason why only one or two 17 year olds have been picked so far.
I'm not saying it should be based only on achievements, just that the two should be balanced out about equally, which is why I suggested the 'who would you be most excited for us to sign' criteria - though I think the teams that would hypothetically fit together best on the field should also be rewarded. Surely it's about finding a blend of great young players throughout the world and forming a team that can face off against everyone else's, otherwise how do you judge people's draft teams head to head?