I run into this issue each year.
By the time someone on here has been awesome enough to edit various structures within the game, it is generally December or January.
The other issue is that EA release their game in October so you are behind to start with.
If EA were crazy enough to release an expansion instead of a new game each year which included stadium creator, tournament creator, new kits and roster updates, I would be amazed, thrilled and needing the pinch myself. I've run into this for so many years.
To be honest, I have never been overly concerned with the rosters, I simply have often made sure each team sits at a certain level when compared to others. SPL may go down to 60, Div 1 = 60-50, Div 2 = 50-35, Div 3 = 30 - 20, Highland League = 25-15, EoS = 20-10, SoS = 15-8, Juniors (Level 5) = 16-8, (Level 6) = 12-5, (Level 7) = 8-3, (Level 8) = 5-2. I am big on the right names for players, but likenesses and faces have rarely been my concern. I someone was happy to make the players look right (like Kaps has done), then I'm happy to make the kits, logos, adboards etc, though not the tournments.