Feature suggestion: There could be a PIN-lock feature as (e.g.) the Telegram app has (on Windows10 at least). The browser would lock itself after several minutes of inactivity OR would keep the browsing history always locked until the PIN is entered. Browsing history, URL suggestions, password manager, and even downloaded files might be encrypted and only viewable after PIN entry. Anybody gaining control over the computer would not be able to look at these data. Investigative journalists, activists, people living in countries with corrupted police, or higher crime, etc. might welcome this. (This feature might be expanded to situations when the user does not log in in N days.)
Feature bounty incentives suggestion: On occasion companies reward bug hunters over Bug bounty program. I suggest starting a Feature bounty program (probably some BAT rewards) to motivate the users to think and contribute. I believe people would come with some pretty good scenarios e.g. with using the tokens within the browser, etc., when somehow motivated.