)
I really can't see why you'd ever want to turn on that functionality. It goes directly against the definition of implication and is basically unusable outside of some edge cases.
If you want to stay with the Flutterdash example (or any other ship involving a female character, for that matter), hiding/spoilering the implied @`female@` alone would affect over 1.3 million images featuring a female character regardless of context. That's over half of the images on the booru. Because of a single ship between two specific characters.
If you want to use a feature like that only for tags that imply a single, small(-ish) tag, then just manually hide/spoiler that tag and you're done. Like, going back to your original post, just hide/spoiler incest and you don't even have to do anything about applecest anymore, since all the images with it are hidden/spoilered due to the implication anyway.