I agree that the same principle could bring decision-making down to a highly-localised level, which could actually be a very good thing, but, again, you are just technically wrong to suggest that Scotland is an arbitrary region:
It entered the union as Scotland, legally it is bound to leave the union in the same form. Whether the Shetlanders later decide to push for independence is a separate issue.
As it stands, you've chosen a tough position if you want to argue that Scotland is not a very distinct country. Bear in mind that they already have an entirely separate legal system, consumer laws, NHS, educational system etc. More importantly, they overwhelming self-identify as Scottish, regardless of whether they happen to be voting yes or no in the current referendum.
Wales may push for independence at some point. Perhaps Cornwall might care enough about it too. The most interesting independence question, however, is England: I have yet to meet an Englishman who has a true sense of what his country is or how to square the massive difference between London and the rest of the country.
By the way, you are wrong about the control you think we have. Yes, we get to send MPs down to Westminster, but that did not do a thing to stop the massive moral and financial tragedies of Afghanistan and Iraq, which the Scottish, right across the political spectrum, where overwhelming against.
We also have no say in the storing of Europe's biggest arsenal of nuclear weapons just a few miles down the road from our most heavily populated city. No English region would agree to that (would you?), but the Scottish MPs are always out-voted 10-1. That is not democracy.