Sorry this comment isn’t actually about Opera, but if you’re a vi* user you might find the Firefox extension Vimperator interesting :)
I find browsing without using my mouse significantly more efficient. I particularly like vimperator’s f command (follow hint), which allows me to type f
(I won’t try and tell you about Firefox extensions that do the other things you’ve mentioned as I’m sure you’ve heard it all before, and I’m not sure they actually exist for all of the cool features you’ve mentioned)