I prefer to have features like this in core so I don't have to give a ton of permissions to a third party. I hope it becomes powerful enough to replace uMatrix.
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/AMO...
If the review process is still insecure (That is how I understand you reply) I would prefer them to put their energy into this. Analyzing popular extensions in depth (and giving them some 'in depth analyzed' badge) so you do not have to trust a third party.
>Add-ons built on the WebExtensions API will now be automatically reviewed. This means we will publish add-ons shortly after uploading. Human reviewers will look at these pre-approved add-ons, prioritized on various risk factors that are calculated from the add-on’s codebase and other metadata.