This is almost the very definition of a meta-tag, so ... no.
Almost all the arguments against any meta-tag tag apply to this proposed tricky-questions tag as well.
I think the [subjective] tag is useless at best and actively harmful at worst.
Useless, because for all the talk about filtering by or filtering out subjective questions using that tag, it’s a poor tool for the job simply because the criteria for its use are, well, subjective. I can tell you what a poll is, or a FAQ, or a list, or a getting-to-know-you (GTKY) question… But where the border lies for subjective I cannot say.
And harmful, because there are some users who actually believe that, like community wiki, it’s some sort of magic that allows you to ignore the normal posting standards.
It’s been used pejoratively and defensively, without any real consistency, for a long long time now. Time to go.