TL

“Second, what should Timothy do with other couples who might be in the same boat?”

Well, you would use the example of this couple as an idea what to do with anyone else that had the same problem. We do that with all of Scripture. All of the real life examples are for our benefit to learn from. I wouldn’t go so far though, as to say that Paul gave a fictitious example. However, you could assume that Paul made a point to speak of them because there were others doing the same. That is a possibility.