So I read Are “close as duplicate” votes being timed out too quickly?, and it got me thinking about close vote expiry. Under the current system, your close vote is not refunded if it expires (that is, you may not vote again on that question). There's a feature request to change that, but that's not the point here.
Point is, if a question repeatedly attracts lonely close votes which expire, it may be a close-worthy question largely slipping through the net. What I'm proposing is an automated 10k-visible flag on questions that have a large number of close votes expire (say
>= 6). This would raise the question to 10k and moderator attention, allowing it to attract the necessary number of votes to actually be closed.
The problem of questions that aren't close-worthy repeatedly triggering the flag would be solved entirely by making it one-time-only - if the 10k brigade doesn't think the question is worth being closed, clearly it isn't.