Something I've thought of fairly recently, is the lack of opportunity to start as an assistant.
Correct me if I'm wrong and have somehow missed this feature, but presently I believe you can only manage a club and not become an assistant.
A lot of people play this game for the realism of starting at a lower league club or unemployed, getting offered the position of manager and working up to the top. However an added element which would be a huge benefit to the game, would be the ability to start as an assistant manager.
That way, you could take control of Reserves, or U18's fixtures, and if you make a name for yourself, you could then progress into full time management.
At the same time, you would be able to recommend some of the younger players to your manager, and help groom some of the exciting youngsters (or unhappy reserves) at the club whilst using all the player interaction you would as a normal manager. Maybe expanding further, if the manager sacks or leaves for a different job you could get the opportunity to go with him (or be sacked too). Manager interaction could also become important as you build a rapport with someone who could potentially be a rival in the future.
The functionality is almost already there in the game for this to happen (ie taking control of reserve/youth matches), but of course there are many possibilities.