If William Shakespeare’s Macbeth had been written in the language and setting of 21st century Scotland, how and why might it differ?

If Shakespeare had written and set Macbeth in modern-day Scotland, it's probable that the issue of Scottish independence from the rest of the United Kingdom might be the backdrop for the action. In 2014, there was a referendum in Scotland on the issue of independence. It was a close contest between those who campaigned to stay part of the United Kingdom and those who campaigned to leave. In the end, 55% voted to stay. The issue of Scottish independence has since come back into the spotlight, because Britain voted to leave the European Union in 2016. This means that Scotland will also (as things currently stand) be leaving, even though 62% of people in Scotland voted to remain. Many people in Scotland feel resentful toward England, as they are being potentially pulled out of Europe not because of how they voted, but because of how the English voted.
In this context, it is perhaps unlikely that Malcolm and Macduff would, in a modern retelling of the play, regroup and gather armies in England; this might bias many people in a Scottish audience against them and undermine their status as the heroes of the play. Alternatively, if Shakespeare was writing the play today, he might choose to write it for and pander to an English audience. Accordingly, he might perhaps cast Macbeth as an advocate for Scottish independence and Malcolm and Macduff as fighting for Scotland to remain a part of the United Kingdom.
As regards the language of the play, there are lots of words in the original play which would now be deemed archaic and replaced with modern equivalents. "Alas" and "alack," for example, might be replaced with more aggressive swear words, and "anon" might be replaced with "right now" or "straight away." Also, "cousin"—which in Shakespeare's time was used to refer to a close friend—might be replaced with "mate" or "pal."

If Macbeth was set in the twenty-first century, it would be a very different play. Firstly, Scotland no longer has a monarchy. This is due to the Act of Union, a piece of legislation from 1707, in which the kingdoms of England and Scotland became one. A twenty-first-century version of Macbeth, therefore, would feature the English monarchy and, most likely, take place in London. Alternatively, it could feature a Scottish nobleman who murders the English queen and takes the throne for himself. Accordingly, the character of King Duncan would be transformed into that of Queen Elizabeth II.
In regards to the language, a 21st century Macbeth would look and sound very different when compared to Shakespeare's version. Words like, "thou" and "thine," for example, would be replaced by "you" and "yours."
In addition, we could expect the battle scenes, like those in act 1 and act 5, to be replaced by more modern examples of warfare, featuring guns and tanks instead of arrows and knives.