I think you would only get a good performance with this if your OS supported file update notifications (which I guess is a feature that is spreading).

Probably need an API where the app calls for notifications of a file update, and a callback to notify the file has been updated? It would also need to be clever enough to not get confused by saving an updated snap/disk etc.

If it is nicely wrapped up in compat/ I am sure it would have a decent chance of getting accepted.