But these are applications for knowledgeable users I think which is not the type of users the GGP is talking about. For these it might be ok to ask for permission. Or to grant it automatically if you are root or sudo'ed. And many use cases could get around with allowing silently to write if the file has been previously been opened by the same application.

Well, of course, sandboxing is opt-in, and there are still lots of programs out there that don't use them.

I'm not sure Emacs or vim, as an example, would ever be able to be sandboxed from the filesystem.

Aquamacs seems to use the system dialogs with no trouble.