Firefox should ask for primary password/system password only when you want to view the passwords in about:logins, not every time when you open the browser . This thing it's already in chromium browsers, when i click to view the password.
Let's be honest. For example my pc is opened and someone wants to look for something online, they don't know my system password (pc password) and asking for the primary password when they open firefox is unacceptable, they can view my passwords afterwards. Primary password should be asked only when you want to autocomplete a field or to view passwords.