Next is the next best thing. Instead of making your browser the environment, think of it as a fantastic browser extension for Emacs.
You can use the SLIME Emacs extension to connect to a running instance of the Next browser. Then, you have complete programmatic access to the full browser data structure through a REPL in Emacs (eg: switching tabs by using shortcut/command in Emacs). And Lisp REPLs are awesomer than something like ipython!
Keyboard driven browsing is now the least imaginative thing possible.
Take the high-quality tools you have for processing text, and apply that to your browsing workflow! Imagine being able to integrate your browsing workflow with your information management system, eg: org-mode. Switch to a project, and with a couple of keystrokes, open the relevant links on a page in a set of browser tabs/buffers. Filter all the HN pages in your browser and bookmark them to a text file (to be resumed later). Save all arXiv pages to your reference management system (eg: bibtex), etc. When browsing webpages, evaluate code blocks (via Emacs). Download/cache videos for all all Youtube tabs you have open. Emacs becomes the IFTTT-like glue for all your browsing activity!
For some chatter/ideas along these lines, take a look at this Github discussion: https://github.com/atlas-engineer/next/issues/195