1) Swiftype (or any of Algolia's integrations - WordPress, ZenDesk, Shopify, Magento, ...) - here you talk about Algolia's developer focus, but the rest of your arguments are about the consumer experience. All search engines are built by developers/engineers, and Algolia delivers end-user experience on Twitch, Periscope, Medium, and even HackerNews (hn.algolia.com), which are exactly what you're looking for. You can actually use Algolia to create all the search engine experience ideas you have, and it takes less time (which you don't have)
2) Mention (http://mention.net)
3) Jelly (didn't work. Maybe there's a reason?)
4) Google / Wikipedia.
Unless you can build something 10x better than what exists,