What I would do is bring back skill boosts during to it being hard to get a player to a secondary position is hard enough already this would be able to have variety of players and where they can play. you can still keep the way the overall goes down in secondary positions but make it the default. On the same topic of variety using skill boosts would increase different squads and player to play with after every new upgrade, forcing players to keep players for a more in depth roster instead of having all of the same new program which gets tiring due to the fact that they only come out every few months. Using these old pleyers for a long time and adding new players would increase diversity in a team and would also have player go for a more technical meta / approach instead of everyone having the same cards for the same reason. You did a good job of bringing back training transfers , which I think could be done and increase every players experience.