Hi Julien,
Just wanted to follow back up on this. Regarding the transitional material, it's not that it was bad material. The problem you had is one every composer has. We spend days or weeks, even months, living with a piece of music. We become intimately familiar with the material. So, when we're trying to do something interesting, it's tempting to reach for a new idea. That is interesting for us.
Now, put yourself in the audience's position. They are hearing your piece for the first time. Every idea is new to them. They do not know what's important. In literature, Anton Chekhov stated this principle by saying, "Remove everything that has no relevance to the story. If you say in the first chapter that there is a rifle hanging on the wall, in the second or third chapter it absolutely must go off. If it's not going to be fired, it shouldn't be hanging there." In music, we make sure that each new idea we bring into play has significance in the piece.
Now, you could drop an idea into a transition and pay it off later. But in the case of this piece, the form is so tight otherwise I think you would create other problems for yourself by trying. But it's a handy trick to think about when conceiving a larger work.