Yes, I know the title of this thread sounds absurd, but hear me out.

I was watching a clip from Maze Runner recently to see what Will Poulter was looking like these days, and unfortunately, I highly doubt he'll be returning to Narnia. However, I saw another boy in the film that looked rather Eustace-y to me and a possible recast for the role. The actor in question is Thomas Brodie-Sangster, who is twenty-five but doesn't look it at all. I showed a picture of him to my brother and asked him to guess his age, and he put him at about fourteen or fifteen.

I don't know whether or not that particular actor would be a good fit, but the idea of deliberately casting older yet very young-looking actors in the roles of Eustace and Jill is somewhat intriguing to me. They wouldn't necessarily have to be in their mid-twenties, but just old enough to know that they're probably done with growing. After watching Will Poulter outgrow his role so quickly, I'm a little concerned at the thought of casting two kids for The Silver Chair and then having the same problem all over again.

Theoretically, this shouldn't be much of a problem if The Last Battle is made directly after The Silver Chair. However, my impression is that most fans would like MN and HHB to precede LB, and Douglas Gresham's desire to see all seven films made may also require that order. If those two films are sandwiched in between SC and LB, then there could easily be four to five years in between filming for whomever is cast as Eustace and Jill. The kids could grow up and we find that the visual in The Last Battle is three adults opposing the Calormenes instead of one man and two teens.

Is this enough of a concern to warrant casting youthful-looking adults in these roles? I'm not sure. One negative that I can think of is that an adult actor playing a much younger character may ring false and detract from the role. However, a very good actor may be able to make the character entirely believable and actually bring more experience to the table. I'm also reminded that we've already seen something similar to this happen in the Narnia film series—twenty-six year old Ben Barnes being cast as Caspian, although it appears that Caspian in the film was aged to be about sixteen or so.

Any thoughts?