We need to play a 4-3-3 but we need to play with the triangle point at the defence. A single deeper player. That is the system that best suits I would say best suits the majority of our players, its also the system which give us the best stability. Not sure about the selection, benefits to all of Morgan, Fellaini or Herrera. Morgan will struggle while Fellaini is on form, Jose would probably prefer the second half of the derby system, extra height and presence.
If that happens Rooney's favoured position disappears, so he's either got to play 9, RW/LW or as one of the 8's. So many managers to know this and show this, Moyes played him a 9, Roy played him wide, LVG played him in midfield and Jose 4 games in has already played him wide.
With Rooney its successive managers failing to accept that he doesn't bring enough to the team to justify weakening the team to accommodate him. How many managers now have accommodated him either into their system or more often their system to him, and in how many of those case have their been rewarded justifiably.
Watching managers over the years, I've basically come the the conclusion the vast majority of managers are tactically aware and understand where that the problems are. The difference between failure and success is whether managers are able to accept central beliefs the hold are wrong or not. Its just whether or not they are willing to let go of an idea that is holding them back. At the top level most managers who struggle will do it for short periods but later return to it, while lower down they tend to stick until they get fired, possibly due to lack of resources. I think more about the mental workings of people than anything football specific. Same reason so few manager stay at the top of the game tactically, as the game evolves but they still stay wedded to tactical beliefs or foundations.