I think a youth league would be better and more realistic than these random rush tournaments. Also, they should add an option to simulate these as well, as I am personally not that interested in playing with the youth players while they are still in the youth team and it is very time consuming and disruptive from the actual career mode. Does not need to be any official league imo, as the age gap between the youth players would not make any sense anyway, or you would need several youth teams for each age group.
I also agree they should add the option to add playstyles via training in career mode.
In addition, they have to finally add the option to edit Composure and Def. Awareness plus playstyles for created players.