One bit of feedback I have is regarding this specific point in the proposal:
We propose changing the string that
#fileevaluates to. To preserve implementation flexibility, we do not specify the exact format of this string
I think in practice the format of the string that is chosen will become the one that is expected by users. Tooling will be written around that expectation.
My preference is we make the format precisely defined. I do not see the value of leaving the format not fully specified, as the flexibility will not exist in practice to just change the format at any time.
Making the format of the string specified also potentially allows the creation of tooling that maps from the concise string to a richer one (e.g., what would be the output of #filePath) with more information. That gets the benefits of conciseness, while also providing a trajectory for supporting good tooling support around the cases that will use #file.