Currently your staff in the game are just there, you have no way of communicating with them and form a relationship. Having for example an assistant manager that you’ve hand picked yourself adds nothing but their coaching abilities. I want to have that close and personalized contact with, especially, my assistant manager, otherwise who they are and what they bring really doesn’t matter. Having a discuss system like you already have with the players would be great. You could discuss certain players, potential transfers, training etc. And if you show your staff enough trust they will start liking you and your relationship will show up at the relationships list.
Addition: Would also be nice if your relationship with your assistant manager boost your managerial skills. Meaning if you have the same assistant m. for a long time and form a good bond with them they start to think like you and help you with new ideas etc. Having this great relationship would mean that you, as a manager, become better because of the insight and thoughts that your Assistant m. gives you!