As for Orkney, the Borders etc voting against indpendence - this is not about parts or regions of a country, it is about the right of a NATION to self-determination. For unionists to embark on "divide and rule" tactics would show just how desperate they are becoming.
Yes, but what is a "nation"? Isn't it just an arbitrary and sometimes fluid geo-political partitioning that is the result of many accidents of history? Scotland ceased to be a nation in the usual sense 300 years ago (except, of course, in certain contexts, sporting endeavours, etc.). You might still like to think of it as a nation, others may prefer to think of it as a constituent state of a greater union. Who's to say who's right?
And anyway, if you go back far enough you'll find the Kingdom of Scotland used to end at the Forth and Clyde. South of that were the lowland kingdoms of Strathclyde and Northumbria. If you want to turn the clock back to the 17th century, why stop there?