I’d really recommend not doing that. Personally, I find the toggle really important for reviewing my posts (both in the preview and after posting) to make sure I blurred everything appropriately. If it was one way only, once I unblur the text to actually review for typos I’d have no choice but to refresh the page to double check the blur locations. And often I do this multiple times (as I make edits), so having to refresh every time would be really inconvenient.
That said, if you’re just talking about making image unblurring one way, that’s probably not a big deal. (I posted my reply before rereading your post, so I think I missed some context, but it can’t hurt to emphasize the usefulness of the toggle in general, even if it’s not terribly important for images.)