Retool, to reorganize or rearrange, usually for the purpose of updating. (dictionary.com) Using retooled to describe what was done to Brandon’s character in S&S3 was in no way meant to be derogatory. It fit the idea I wished to convey and it gave me a little chuckle so if you are amused as well then I say all the better. S&S3 Brandon is by far not the worst retool in Austen adaptations—that honor goes to MP2’s Evil retooling of Fanny Price and Sir Thomas Bertram.

This is a guess but maybe the powers that be cut the dialog about the duel in S&S2 because they wished to drop the duel from the story. It would be better kept in but leaving parts and characters out of adaptations is more like business as usual for film and television folk than not. It seems they live to vex us! I think cutting the duel denies Brandon this final dramatic surprise in his confession; that he is the kind of man who is willing to risk injury (at the least) and defy law and order for what he feels is a just cause. I do not think the changes to Brandon and Eliza’s backstory is necessary but it works in the movie despite its new character. I think Brandon is full of hidden passion and ardor because AR is an excellent actor. His search and carrying Marianne back to Cleveland is the act of such a man. I found an interview of AR where ET says he is slightly dangerous; it might be the one you are looking for:

http://articles.latimes.com/2011/nov/20/entertainment/la-ca-alan-rickman-20111120