I have no idea what this RfC is talking about. It seems to be a duplicate of m:Requests for comment/Global bits and pieces but then I'm not sure why it's called "Global scripts". There is a section "Existing" which talks of totally unrelated things, then "Scopes" which is not about scripts.
I suggest to make it an RfC about global templates or about global gadgets. Any RfC about global templates is useless until someone enables and tests $wgEnableScaryTranscluding somewhere, reporting back with field-tested issues rather than philosophy.