The thing I'm most curious about is how far Kathryn would've gone in certain scenes if Luke didn't stop her (park kiss and alley grope scenes for example, she needs to know what is going on for these scenarios), the cops didn't arrive in the forest, Alex could hold off on cumming for longer, the metro didn't arrive at her station yet, etc. Keeping her inhibition level the same as it was at that point in the story so it's more realistic to her character and mood at those points, so scenes where she refuses to go further herself would stay the same.
What-ifs that keep the character the same but just change a single thing about the scenario are the most interesting.