To have the ability to self host your own Firefox addons instance. To be able to self host your own server for hosting Firefox addons.
And to have the ability to add/remove Firefox addon repositories in the Firefox settings. By default the only Firefox addon repository is the official Mozilla Firefox addon store.
When a user adds a repository, they will be warned that downloading addons from a 3rd party repository could be malicious.
This will add more decentralisation to browser extensions in general by allowing anyone to self host their own repository. Similar to how it is possible to self host you own F-Droid repo for Android apps, or Scoop bucket for Windows applications.
This will be a great feature to have on Desktop and Android Firefox.