This is a complicated approach which adds unnecessary UI overhead. We already support local storage based autosaving that works in parallel to saving to the server. On save it does both, on restore it first checks local, then checks from the server.

It only activates an autosave after a minimum number of keystrokes (I can't remember what exactly) and only on certain fields.

If there's some kind of bug there, or some use case where major amounts of work are likely to be lost, there'd need to be an issue saying what exact form it happened on, and confirmation autorestore wasn't successful.