Sorry for letting this one stale, I am (maybe overly) cautious about what I think would be the right way forward, and wasn’t too satisfied with this approach. That’s why I played with an alternative idea (Inlined typed dicts and typed dict comprehensions - #12 by Viicos / PEP 9999 – Inline type expressions and inline typed dictionaries | peps.python.org), and together with Idea: Simpler and More Expressive Type Annotations / PEP 827: Type Manipulation it might make this PEP obsolete.
But I do acknowledge the demand for this one, and maybe it isn’t that much of an issue to have this syntax and potentially a more idiomatic one in the future?