One thing that might release some of the pressure around addons would be to make Gecko more embeddable, the way Blink is.

We've started seeing a lot of alternative Blink UIs (Brave, Vivaldi, new Opera, etc) alongside apps built on it via Electron. Those alternative UIs do things Chrome extensions can't, even including things Firefox 57 lost the ability to do.

I don't know how close to that state Gecko is right now, so maybe it would be less work just to recreate the necessary APIs like they're already doing. But if not it could help bring back some of Gecko's market share, which is at least as important as that of Firefox as a whole.