A few problems with this suggestion:
Just because philosophy includes metaphysics does not mean we need anything different than StackOverflow which has metaprogramming as a sub top topic or Cross Validated which has meta-analyses as one of is sub topics.
Meta.PSE is perfectly suitable for all levels of meta questions. The important separation is between the ...
Let's leave aside the meta-ness of the simple tag. The other problem with it is that every question and every good answer to every question should be "simple" - it should not contain superfluous details. It should get to the point. It should use technical terms when necessary (and provide references to more obscure technical terms or references).
The end ...
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