I would strongly disagree on the sysadmin stuff. Firefox has always had a very powerful settings system. All the stuff you could set in about:config can also be set via a set of configuration files provided by the sysadmin, the user and the distro, each of which can provide defaults, presets or locked non-changeable settings which are hierarchically enforced. Exactly what you need as a sysadmin, cross-platform, could do everything and the kitchen sink, distributable either via your usual config management or LDAP/HTTP/whatever you can script in a few lines of Javascript if you need. GPOs are just a poor windows admin's substitute, they cannot do half of that, even in IE and Edge. Not to mention Chrome, which lags miles behind there.