I don't know what 3diddly prefers but your proposal opens another branch. This would mean all renders have to be adapted to a 'fitness model' and this would mean some extra work (and time) for the dev. I argued here against incest and beastiality because it doesn't influence Katie's corruption, so I don't think that a 'fitness model' path makes sense. Please keep in mind that people expect corruption, to what stage and direction ever, in this story. What you'd like to see makes a theme for another story.
I think I understood your concern, but even if I'm not too keen on the technical aspect of creating this types of games and their system of variables, I actually don't think that would be a big of a problem. She would get her body modified a bit, but I think that is a transformation similar to all those she has been through already, like getting her hair changed or getting a piercing or the different types of dresses. And in my way of looking at things, it would not open another branch, it would just be her natural progression in the pure corruption path, it's just something she would do along the way. But then again, I'm no expert on the process of creating a game such as this one and its technicalities , so I don't know the hurdles of doing that.
Regarding her body change specifically, I also don't want her to become over fit or with too much bulgy muscles all over her body as 3Diddly said, I just want her to be a bit more toned and worked in the right places, especially her butt, like those so called instagram fitness models that became "famous" just by showing and sharing their round, juicy ass to the world via social media.
And actually in the gym scene, Vera explicitly told Katie the routine for her to follow, and that this cardio to burn fat, squats for the gleuts to make make her ass big and juicy, and yogga applied to the core for the abs. It's not an overall workout.
I do think it would be a nice and suitible change to her, and I would not mind if she could become a bit more bulky too, it would really highlight and display her transformation. Her model as it is right now is already rather lean and fit.
Look at how much has been written about the motivations of characters in the plays of Shakespeare. WRT HC, myself and other patrons had some great discussions about what was going to happen and what we would like to see. Similar to what @othello says, I feel perfectly fine commenting on inconsistencies in stories. No I am not expecting it to change anything in a completed story (not quite that delusional) but I think it makes for a better story-teller if such things are discussed in a forum where the writer can read them (if they are presented without vitriol). I don't think this is commenting about characters not acting like we want them to, it is commenting on characters acting counter to how they themselves are presented.
