As with the Scottish Referendum those campaigning to keep the status-quo can really only highlight what would be lost as the benefits are already been conferred. I think, like the Scottish Referendum, to dismiss that as scaremongering is disingenuous. How are those in favour meant to campaign to stay in if they can't highlight what would be lost?
Still maybe the Stay campaign will learn from Better Together and try and fame the conversation more positively, it's helps they've kept the 'Yes' option this time. The fact they will probably have 'a deal' at the start of the campaign will help too but the migrant crisis has come at a bad time for them.
I think the Yes campaign does have a case though, it's not one that would find an audience on here. This Economist article, from a few years ago now, highlights some of them:
http://www.economist.com/news/leader...ld-be-reckless