.onion is not a TLD. I've seen it classified as a "psuedo TLD" but either way.... dot onion would be a horrible substitute to anything mentioned in the comments. the user base for tor/oninion is catastrophically smaller and the requirements to view a .onion site reaches a little further than the general public can take. think of how many people don't even realize there's VERSIONS of internet explorer and have never upgraded. cringes