There is obviously no right or wrong answer and I know many of the examples, short of Northern Ireland, are realistically unlikely. It's more about questioning just where someone draws the line. I find that people who argue for independence or some form of self determination at one level nearly always refuse it being taken one step further (eg the Scots would think that splitting from the UK is a viable form of self-determination but highlands splitting from the lowlands isn't). Go back in history far enough and the highlands had an identity that was distinct from the lowlands and in an independent Scotland there is nothing to say that highlanders may not feel they get a raw deal and think actually most of the oil would be in highlander rather than lowlander waters for example.
It also begs the question of what constitutes a unique identity. Scots may define themselves as unique form the English but imagine you took some random Scots and random English, didn't allow them to discuss anything specifically involving their country and hid their accents, would the really be able to tell who was Scottish and who wasn't without making some comment intrinsically linked to nationality? Could they point to how their lives, culture, world view, loves, hates etc etc are so fundamentally different as to define themselves as a separate people? NOTE I do think the Scots are distinct from the English but usually it's just asserted as such without any real justification why, just that it is.
