I think this would be a fair change and compromise.
Because logged in users can toggle both the NSFW Blur and the Auto Expand in their account settings it doesn’t seem as if it would significantly negatively effect current account holder users.
I suppose if there’s a userbase that utilizes the site without an account or without being logged in on a regular basis this could hamper their experience, but I guess that’s where the big question is. Would such a change effect the conversion of non-account holding users to account holding users on a positive, negative, or neutral basis?
I’m no marketing or analytics person so I wouldn’t know what sort of data would be needed to determine that, and if it’s even available in the current site version, but either way I don’t think there’s any way to tell other than making the change and seeing what happens.