In my case it's both squads for both sides, but this isn't just about me. It's about everybody managing in the game.
If you look at G101, Barry has Man Utd. They are the best team in the game and his youth team are also exceptionally good... so it doesn't affect him if these changes stop him buying youth players for 6 months or 9 months. I'm sure that isn't why he's saying don't change things, but all it does is allow his already great youth side to get even better while those that can't sign players to strengthen stand still - and thus drop back even further. As it is, if Man Utd sign a 17/90 they probably won't even get a game in the youth team whereas Chelsea sign a 17/90 and they are in the first team.
What would effectively happen is those clubs that have been managed the longest and have had the most time to build a decent youth side will create a monopoly that will prevent other teams from being competitive, because by the time they have got level 5 facilities, the other clubs will also have level 5 facilities, and their youths from before the change will be 12 months of training better off... so I could sign a 17/90 now, but the 17/90 that Barca signed the day before the change could easily be a 94 or 95 by then.
It would be saying that G101 isn't worth playing for people that haven't been in from the start because there is no incentive to join or stick around because you can't develop a youth setup to make you competitive for the best part of a year. Would I walk from 101? Yes quite possibly, but not because I'm throwing my toys - it's about can I be bothered to stick around for the best part of a year to try and catch up, knowing that in a year I will still be lagging behind because of all those sides that had good youth sides before. I'd be reduced to the old TATT equivalent of ticking the "same team as last time" box every week for a year.
The simple solution is that this only comes in for new games, but that isn't practical.