Duke - a UI is not really central to my point (and UI is something I'm a bit ambivalent/undecided about), lets just go with SF being the biggest party & having the first Minister - which I don't think is that remote over time because whatever about wanting a UI or not, I'm not aware of any strong trend of "nationalists"/catholics voting for unionist parties. Basically the DUP are still using the old playbook but the rules of the game are about to change.
The union crumbling is nothing to do with NI, but its obvious that Westminster is in disarray, Brexit is looking catastrophic, Scots are getting royally (cough) annoyed with power grabs and being dragging into Brexit where they will suffer - so leaving aside any Braveheart facepaint stuff, Scottish independence is veering closer than ever. Should Scotland leave then the UK is effectively done - Wales seems happy enough to trundle away as an adjunct of England, NI will look like a total outlier if its spiritual homeland of Scotland has left the building. Will London continue to foot the bill with the union gone?, I think the pressure for a UI will come from there.
Anyways, I think we both agree that unionism should reconcile itself and get on with the business of getting on, this holding back the tide is not going well - digging in on something as harmless as an Irish language act is a really poor ...well....sign.