There are a lot of small fixes that would make manager mode so much more enjoyable.
1. Transfer funds that roll over year to year.
2. Fix Youth Academy players: particularly their physical stats/growth. Also, make sure they're assigned the right position for their skills. I'm currently playing a RB at striker and a CM at CB
3. Club trophy case: like in CH 2k8, would be cool to have a trophy room you could move around in and look at everything the club has won.
4. The game should track career stats for players, for both club and country. It would be awesome to see my young YA player earn his 100th cap for the national team, or break the club's career scoring record.
5. More national teams: right now, if I'm controlled the USA national team I automatically qualify for the world cup. There should be at least enough teams to hold the WC qualifying for teams outside of Europe. Would create a much more immersive world
6. Ability to edit the physical appearance and position of YA players.
7. Dynamic commentary: If I win the league 3x in a row it would be nice to hear the commentators talk about my history of success and how the club is in the middle of a dynasty.
8. Crowd reactions to specific players: if a player is really struggling or disappointing the crowd could whistle, chant or boo when they touch the ball. Conversely, they might have the opposite reaction to a club legend or a player in excellent form.
9. FIFA XI and world player of the year awards at the end of each season.
10. A history page for the major competitions that records the winners every year. Doesn't have to be complicated. For example...
Champions League Winners
2018: Barcelona
2017: Bayern Munich
2016: Barcelona
2015: Juventus
2014: Real Madrid
etc.
would lend a sense of history and make the MM more immersive