- It must be ultra lightweight: fast when starting up, fast when handling load of tabs, just fast.
- Doing _one single thing_ exceptionally well: enable the user to browse. Built-in modularity means add-ons/plug-ins/etc can optionally be added to expand the browser capabilities.
So yeah: IMO a browser really should be just the browser with a good Addon-On API. That's why I would add a third point to your list:
- The Browser Team should provide (optional) Core-Plugins which are easy to install and in turn provide basic but useful features. For instance those mentioned in other comments here (e.g. uBlock, MAFF-Support, Mouse-Gestures, ...)