The Youth Trainer is a game changer, and as you said we're still figuring out the full extent of those changes. There are rumors of Chinese players have 18-20s on their bigs to start the season. In terms of standardizing having a YT, I think that would be hard to do simply due to cost, especially in lower divisions, much in the same way regular trainer levels aren't really dictated besides Advanced(lvl 4) being the minimum that can typically get a guy on the team. It is advantageous for both the U21 and the manager to use a YT for quicker skill development just like it is better for getting pops by having a higher level trainer.
One of the new staff members that should be standardized and I believe it has been for a number of players is the Sports Psychologist. With our bad luck for Game Shape and just how fickle the coding seems to be, we need to take every advantage to maximize GS on a weekly basis and that's what this staff member does. To me, having a Sports Psychologist or not could be the difference between two similar players making the team, with all else between their managers being equal.
I once had a team with 1757 players and was $25,835,360 in debt. This is not that team. Join the Discord group open to anyone, but especially for USA managers to improve your club or get involved with the U21 and NT programs
(https://discord.gg/cKpNkt2).