So far, we got 3/5, also attributes were re-proposed almost equally by someone else (maybe 4/5), so I'm happy that even though I couldn´t work with that and participate in last years 😞, some convergence emerged 😛!

Back in the day I thought about a "is_first_redeclaration" predicate, I don't know if somebody else considered something like this, compilers probably maintain a pointer to previous declarations in redeclared AST Nodes, so it is probably cheap acquire this info, and even if you get out-of-order function declarations in different compilations units you still can get the same function name and parameter types, even in cases when parameter names are different;

What is written in the proposal p1240r1.pdf page 36 puzzled me :

  "Of note here is that we are not proposing a function to retrieve members of namespaces: Due to their”open scope” nature, we believe that capability is somewhat meaningless. There is however no known technical reason preventing us from doing so."  

I interpreted "meaningless" in the sense of "not useful", by the previous answers I presume that "yes it has good uses" and also there are known technical issues.