Making host permissions optional by default will introduce another prompt, and a new state where the extension is installed but isn't actually able to do its job. However, users do not read prompts and are already confused by extension icons being hidden by default in Chrome/Edge and easily lost in Firefox.

When a user installs a privacy content blocker or a password manager, the user does not want to wade through multiple prompts just to get the thing to work. Yes, it's good to offer control to users who want it. However, the general user does not want this ability, the general user often does not know how to find the extension's icon. The general user just wants the extension to work.

It's not at all clear how this will curb malicious extensions, but the potential to further confuse users is very clear. Consider that malicious extensions will and do come up with wonderful on-boarding experiences.

Additionally, how will this interact with Selenium/Geckodriver/Chromedriver? Will browsers add command line flags to auto opt into all permissions?