I agree that it could give another look at Susan and help people understand why she ends up the way she does in LB. It's a chance to really flush out her character. HHB is another chance to help develop Aslan. It shows his goodness and yet his untame side which should be highlighted before LB as well. When all is said and done in LB, it would look pretty strange for the characters of Aravis and Shasta as well as all of the others to be there if HHB is left out. Personally, since it's a 7 book set it should be a 7 movie set as well. It wouldn't be right without it. The set of movies would always be a little lacking if any one book were cast aside.