Derrick Stolee wrote:

Singular "you" had a similar backlash in the 1660s as singular "they"
is having in this thread, but singular "you" has lasted (and we use
"thou" only to signify someone using old-timey language).

There is more of this in [1] and [2]

[1] https://public.oed.com/blog/a-brief-history-of-singular-they/

Let's see...

  In modern English, that’s: ‘Each man hurried . . . till they drew near
  . . . where William and his darling were lying together.’

Yeah, that grammatical singular "they" indeed, but with a semantic
plural antecedent, so no, that's not what you are proposing above.

I'd say leave linguistics to linguists.

-- 
Felipe Contreras