So basically, expansion on the base game it self.
I've seen quite a few such suggestions on Twitter specifically. Added to my notes!
So, other than the way the engine does it's calculations you would like to see some greater variety as to the individual (and whole-team as well I presume), performance of the players. Specific instructions to specific players.
Some more complexity that should provide greater strategic play and execution from the Managers.
Hm, maybe even the addition of more specialized roles for players. Example: A Sweeper role/specialization for Defenders.