How serious was Rhaegar about deposing his father?
The last time Jaime and Rhaegar spoke, Rhaegar said this:
Rhaegar had put his hand on Jaime's shoulder. "When this battle's done I mean to call a council. Changes will be made. I meant to do it long ago, but . . . well, it does no good to speak of roads not taken. We shall talk when I return."
Those were the last words Rhaegar Targaryen ever spoke to him. Outside the gates an army had assembled, whilst another descended on the Trident. So the Prince of Dragonstone mounted up and donned his tall black helm, and rode forth to his doom.
He says he meant to make changes. Meaning to do something and actually doing steps in order to get it done are two different things. I've been thinking about this specifically around the arrest of Brandon Stark. Did Rhaegar know that happened? Because the time until Rickard gets word and arrives at KL would take over a month. Maybe even two. Why didn't Rhaegar act then?
The tourney at Harrenhal was believed to be an occasion to make plans. What even came out of that? If you really want to, you can get active pretty fast. Daemon Blackfyre had his ducks in a row, Bloodraven found out and things popped off. Robert, Ned and Jon Arryn immediately made moves once they receive the threat from Aerys.
If Rhaegar made no actual moves to set up this coup, how serious was he about it, really?