Imagine a more powerful API existed that an extension could use to control other extensions. Now the badware extensions start using the more powerful API and you're back to square one...
I'd like the ability to put an extension of my choice in a privileged mode so that it could escape such limitations. But sadly, given such feature, the usual response of asshole evil developers will be to ask users to give privileges to their extensions for "enhanced experience" or "to ensure that the extension works properly".