When editing an answer, I sometimes want to lock the answer while I'm editing.
I'm proposing a new feature here : Make posts (answers or questions [without answers on it already]) lockable.
This would be an SE-wide change which you would to rise on Meta.SE. But the system already locks a post while it‘s getting edited, so I don‘t see a benefit here. If you do multi-step edits, you can always delete the post while doing so.