Since it's not my money, I'll continue my journey into fantasy land.
Beyond U18, there is little for the National Team to gain by keeping the net wider than it is currently. Most of those top players will be in college the following year playing soccer, and a few will be pros. Keep the U20 and U23 processes in place as is.
In addition to seeing more players overall, the regional national team idea creates competition against players with better skill and overall athleticism than the US youth teams currently see in CONCACAF tournaments. Other than Mexico and Canada, most players get better competition from their club team. The money spent on CONCACAF gives little bang for the buck in terms of competition.
Creativity would be needed to reduce costs. College campus housing is often available in the summer. There is no need for a huge complex of fields as the total number of teams is 24 (6 regions x 4 age groups) so expensive areas like San Diego can be avoided. Local sponsorships would be useful. Consider combining this with 2 USWNT exhibitions to kick off and end the event. Maybe have an NWSL game or two as well. Americans love a tournament and crowning a National Champion. I'd tap into that.
The most important outcome of this for the National Team would be that they would have more influence on training. Six times as many girls are involved. More teams and coaches will be able to tout their National Team players, and more parents will seek out the training that is leading to invitations.