I have been trying _very_ hard to get in contact with the folks that are discussing this approach; just preventing ADL constexpr tricks (through "friendly definitions") isn't enough.
I am still waiting for the relevant parties to reply to my emails, but an article explaining "everything" (and the different approaches (about 3 at the current time, in addition to "friendly definitions") will be published soon.
There is a lot of wording that has to be changed in order to prevent the semantics explained.