Something just occurred to me, that I am not sure if it is viable, so I thought I'd get your opinions.
There's an example in the book, that I will use. It's about the thief who wants to pick a lock in the middle of a battle. He rolls discipline to place the aspect "focused" on himself, to get a better shot at the pick. However, an opposing gunslinger sees him and wants to keep him from placing the aspect, defending with guns against the maneuver.
So far so good. Now to add one element:
The thief has his own gunslinger with him, who put up a block prior to the thief trying to focus.
Now let's say the opposing gunslinger succeeded in defending against the maneuver, so the aspect would not be placed. The block though is even higher, so the thief could have used it to block a similar guns attack.
But could he use it to block the defense roll?
On the one hand, it would make sense, so I'm inclined to allow it. On the other hand, I'm not sure that it's intended that way.