In the past we have had the World Cup add ons, but we've yet to see much develop beyond that. The concept is certainly one that is well received when released and could be continued in another form. There is a portion of the community that does not have the time or money to compete with other teams in FUT or would prefer to get their team the old fashioned way. Introducing a bare bones mode, without a transfer market, could be a great idea for those that enjoy the grind of FUT and can stay on a more even playing field.
Online co-op is certainly something that players have requested for a while. The ability to do it is there, it just isn't included within FUT. FIFA 20 Ultimate Team should include a new dynamic to the game mode and give friends a more social opportunity within FUT. You could even combine players from each club when taking on opponents.
One issue with experimenting on FUT is that you have no idea whether something you've changed tactically has had a major impact without playing a game; you're also unable to try out new players in different scenarios. By adding a training mode, FIFA 20 could greatly improve the user experience, there’s already this functionality in FIFA 20 Pro Clubs, which was recently announced, why not do this for FIFA 20 Ultimate Team?
Playing with friends is one of the best aspects of online gaming and being able to enjoy FIFA with friends can be tough with restricted opportunities. FIFA 20 could introduce a private league system for you and your friends to enjoy FUT while having something to work for that is a bit more personal - they could follow a similar structure to F1 2019 in that regard.