So, I was thinking about the rules as I often do. I thought up a hypothetical that hasn't come up before because none of the people in my play group have try doing the maneuver fighter before.
The situation is that an ally is standing in front of a dragon who has its fire breath charged. I'm on the other side of the dragon not drawing it's attention. My turn comes up right before the dragon and I say "I'd like to hold my action until the dragon aims it's dragon breath. The action I would like to ready is to attack the dragon." Then it's the dragon's turn and the gm states that he will use the dragon's breath attack on my friend, and aims the cone directly towards them. I take my attack and I expend a superiority dice to use maneuvering attack, assuming it hits, and I give my friend half his movement that he can use for his reaction.
Would the dragon be able to re-aim, or would this work out perfectly and render the dragon's breath potentially useless?