Overall this is an argument for treating human identity humanely, that is, as though the human is the most important part of human identity. That is persuasive to me, particularly in contrast to inhumane models of identity that exist primarily to serve exploitive business models.
Facebook Work accounts. Teachers running Google Classroom. There are plenty of examples where technical solutions that address the first problem (to make it easier for computers) exacerbate the second (which seeks to make things easier for humans). We should prioritise the technological solutions that help us, not machines.
Bingo. This is why I want to introduce the worst case scenario for the existing model and propose a system flexible enough to handle that, this incidentally solves a lot of problems that other people have along the way.