I am focusing (perhaps too much) on the tense issues. Without tense, "no password reset mechanism", to continue using the same example, represents a problem state.
If something is a problem, it exists in the present.
If something will be a problem, with any contingency or timeline, then by definition it is not yet a problem.
Even in your own phrasing, the tense issue becomes clear:
> Yes, he doesn't have the problem now, because he's got no users, so indeed, having to reset the passwords of existing users would be a "nice to have" problem.
Specifically "... would be a "nice to have" problem." This indicates that it is not a problem, rather that it can become a problem.
I fully agree with everything GP said, by their understanding of what I meant. But yeah, to be useful the question has to be forward looking. Would things have to change for the better for this problem to actually manifest.
I think you misunderstand his word usage, though you're seemingly following the same process.
A "nice problem to have" is one that results from having success. Yes, he doesn't have the problem now, because he's got no users, so indeed, having to reset the passwords of existing users would be a "nice to have" problem.
You're already in the "nice to have" zone (clients with problems to solve!), and you want to fix those problems brought on by popularity.