Interesting idea but not a good one, most managers don't have 6-10 players who are U23. Also it would could lead to lower division teams(D.II, D.III, D.IV) winning the cup and getting killed in B3 the next season.
But your idea is very interesting. Maybe there should be some kind of youth(U23) cup or competition that takes place on Sunday. The games would have no impact on minutes or merchandise, fan survey,etc. It would be just for fun. It would encourage mangers to have more trainees and have younger guys on the team. Maybe there could be awards for winning, or being the runner up or getting to the quarter/semi final. Maybe free supporter or a certain amount of money.
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