Isolated(any) evolution and current limitations

Evolution Discussion
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It seems to me that SE-0431: @isolated(any) Function Types lays out a future direction to allow something like what you want:

In order for a call to an @isolated(any) function to be treated as not crossing an isolation boundary, the caller must be known to have the same isolation as the function. Since the isolation of an @isolated(any) parameter is necessarily an opaque value, this would require the caller to be declared with value-specific isolation. It is currently not possible for a local function or closure to be isolated to a specific value that isn't already the isolation of the current context.[… (footnote)] The following rules lay out how @isolated(any) should interact with possible future language support for functions that are explicitly isolated to a captured value. In order to present these rules, this proposal uses the syntax currently proposed by the closure isolation control pitch, where putting isolated before a capture makes the closure isolated to that value. This should not be construed as accepting the terms of that pitch. Accepting this proposal will leave most of this section "suspended" until a feature with a similar effect is added to the language.

If f is an immutable binding of @isolated(any) function type, then a call to f does not cross an isolation boundary if the current context is isolated to a derivation of the expression f.isolation.

In the isolated captures pitch, a closure can be isolated to a specific value by using the isolated modifier on an entry in its capture list. So this question would reduce to whether that capture was initialized to a derivation of f.isolation.

[…]

For example:

func delay(operation: @isolated(any) () -> ()) {
  let isolation = operation.isolation
  Task { [isolated isolation] in // <-- tentative syntax from the isolated captures pitch
    print("waking")
    operation() // <-- does not cross an isolation barrier and so is synchronous
    print("finished")
  }
}

Admittedly, I don't understand whether this refers to exactly what you have in mind, but it sounds very similar.

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