The current system works but it is unintuitive and prone to mistakes by players, moving to the wrong province, forgetting to leave the PT behind and so on are frequent in games.
A drag & drop system in which you could first click the march order you wish to execute and then you would get the chance to actually move the pieces in the area to their destinations and create (or not) the PT would be a lot easier to explain, less prone to errors and would make understanding what's going on when you are attacked a lot easier.