I think the idea of opening the U16 and U17 trials to applicants (they have to apply and be accepted) is a good idea - there are just too many kids at that age range that have had little or no national exposure for a committee to have a chance to see them all. That said, the process of selection from 140 +/- to 100 and then to 40 seems awfully compressed, to be cutting a significant number of 'invitees' who got their invites based on observation over 12 months rather than two days in a gym with 140 other players. I would have preferred to see the invitees all make it to the 40-50 player cut and then have 2 days to cut down to 15-18 final group. If you ended up in a section of underachievers at the 100 cut mark it could doom your chances.
The experience for everyone getting a chance to work with and against the best quality age peers has to be a positive - many of them are so far above the players on their own teams that seeing a broad cross section of the national talent is both an eye opener and a motivator even if they last only till the first cut.