Starting with Firefox24 IIRC, it will be possible to assign multiple origins (principals) to a sandbox. This would enable user scripts to define a set of hosts for cross-domain XHR (without the server having to implement CORS).
The add-on SDK already implemented this: https://addons.mozilla.org/en-US/developers/docs/sdk/Firefox-24/dev-guide/guides/content-scripts/cross-domain.html
It might be a good idea, for compatibility reasons, to allow something similar in Scriptish.
@erikvold Any thoughts about this?
+1 not sure if we should deprecated GM_xhr tho
@Domain is used to limit GM_xhr at the moment, it could be used to define the expanded principal too.