I don't like Vivaldi in total either, and although it is the most horrible decision to use Ctrl+q as a combination for that for that, Vivaldi's Quick Filter for commands seems to be a quite nice innovation (it reminds me of sublime-text). Just in case that was undiscovered–I want such a feature for my browser. :þ
Figured out that I have not tried otter way too long. After seeing vivaldi and testing otter again, I know exactly that this browser here is much more likely going to become the replacement of my Opera.
So: I don't know what I can do that makes you go on, but it is impressive how far you got by now. Maybe leave a way of donating so people can show their appreciation of your work?!
- custom shortcuts (including single-key bindings; ability to remove shortcuts like Ctrl+backspace and AltGr+9 {can't do closing brackets using my keyboard layout!) - custom layout (especially refering to http://operawiki.info/CustomButtons and my beloved buttons (turn on/off proxy, turn off/on images, go to certificate settings, online/offline mode, … , probably also enable/disable javascript) - navigation between links via Shift+arrows(any), Ctrl+arrow(up,down) - notes panel - links panel (including search for html tags, multiple downloads) - windows panel - collection of site-specific settings (also add: site-specific caching) - dictionary
- show source code (context menu + Ctrl+u) - show tcp headers (I believe you are on that one?!) - otter:config (plus more possibilites and explanations) - documentation in general