The goal in my mind was to try generating context information for translators as automatically as possible while retaining the usual workflow developers would use in a given framework for localisable resources.

But yes, the requirement to cover every control, menu and dialog as well as every possible code path that uses a localisable string from the source code makes the whole endeavour very impractical to solve. With dialogs built in markup, e.g. Qt's .ui or XAML it's easy enough to give context, but the hard part is strings in code where you never know where they'll end up.