I'm not sure it should happen at random times, nor should it always have a random element (who is involved), mainly, but not only, because I don't think there are enough scenes to allow it (how many times did her stepbrother steal her panties at this point of the story? four or five times? add a random element here and you'll risk never getting every possibility). So, I think it would be best, instead, for it to happen only when her stats are at certain values and go for a scripted scene specific to this point.
However, I definitely agree it is a good idea to make it a useful scene to change one, or even two situations. In my opinion, those should be convincing May to abandon panties, and kickstarting a stepfather side story. But I don't think spanking would be the right scene with her stepfather: it would be far too drastic a change (especially since it would be a butt-naked spanking, by definition).
So, to develop your idea, what I would suggest would be to have the following succession of "missing panties" scenes:
- The first time after her stepbrother sneaks in to steal the panties would happen like you suggest, but she avoids being caught by a hair, forcing her to “retreat” and go commando. If we miss this for an update, that's not important.
- The second time, she does not want to risk it and it happens according to the current script (she dresses immediately and go pantyless the rest of the day) with minimal changes in the inner monologue (to acknowledge why she does not go to the laundry room).
- The third time (with the appropriate stat values), she would go downstairs again and be caught by her stepfather or stepbrother, either as a one-shot (stepbrother) or to start a new side story (stepfather). Missing this one through an update would be more problematic, but maybe a “bonus” scene of the stepbrother stealing the panties could be generated automatically on the first played night after the update if May's stats are too high and the third panty theft has already been executed.
- She would again skip it completely for the fourth, for fear of being caught again (with good reason, since she gets caught every single time with my scenario ).
- And the fifth time would occur only after she gets to go naked in the night through the house, and would involve Mia, convincing her to abandon wearing panties altogether. Like for the third one, a “bonus” panty theft scene would occur if the programmed scenes have already occurred (with a two- or three-night delay if the third time had also to be forced).
This way, it would be easier to integrate a side story about her missing panties. It would also allow Crazybat to give a little bit more substance to the panty thefts through one-shot interactions even if they cannot be integrated in the planned storyline, thus answering your own concerns over this issue.
What do you think?