2. Coaching, it would be good but useless. YOU set the line-up, subs, players, tactic.
Not necessarily useless. This would likely require coaches to be a separate staff role than trainer or cause a lot of disruption, but the game-day coaches could certainly either have more abilities or at minimum a "specialty" that could affect the team's play.
I think the "specialty" version would be easier to implement and likely less imbalanced. A coach could specialize in OD, ID, outside offense, inside offense, flow, positioning, or rebounding for example, with a corresponding increase in gameday performance (I would say positioning might increase effectiveness of zones and give slight increases in rebounding and maybe passing). A more indepth version would be giving ratings to each of these abilities, but there would be issues in balancing it in a way to make it useful but not something where everyone is going out chasing a perfect coach and those who have built up money are the only ones who could afford it, especially with the financial state of the game as it is. A quick thought might be that there'd be levels of coaches as there are trainers, and each level has a fixed number of skill points and then they're distributed in somewhat reasonable manners, and maybe allowing a user to adjust each skill +/- 1 after each full season the coach has been on the staff (with, of course, the minus and plus ones equaling out).
But this is the sort of thing that would need to go on the suggestions forum anyhow and needs a lot more fleshing out before it would be a useful proposal, and then of course it would need to wait for a point in the game where this type of suggestion could actually feasibly be implemented.