Many a times, there are questions which are absolutely vague and have no meaning in them, like: If I fall from a great height, will I overcome the speed of light?
Now, these are off topic questions, but there are no proper flags for this. Generally I flag this as very low quality, but many times, why I don't know, this flag is not available after one close vote has been submitted.
These are not homework questions or do not satisfy any other realm of flagging. So, there should be a proper flag as "not-constructive", so that these off topic questions can stand out, and can be properly flagged.
One can close with a custom close reason, but in case of flagging, only option is to call for Moderator Intervention, but I don't feel such questions are of a minimum quality to call for Moderator Intervention, and disturb them everytime.
The "unclear what you're asking" flag is not a good option, because it is very clear what the asker wants to know, but the question is foolish and has no dedicated answer.
So, there should be a separate flag called "not-constructive", and a separate review queue to handle them.