As you know, the Irish border is so complicated because of the violent (still more or less recent) past on the Isle of Ireland.
I can't see that so troublesome in a case of an independent Scotland.
The history of the Irish border complicates matters, certainly, but it's not the reason it's a problem -- the problem is creating a customs border where none existed before, as we're about to see graphically demonstrated in Kent on January 1st next year, regardless of whether there's a deal or not.
At the moment, traffic can flow as easily between Scotland and England as it can between Wales and England.
Create a need for EU border inspections as Scottish farmers try to export Scottish beef into England or Welsh farmers try to export Lamb into Scotland, or supermarket chains try to move goods from English warehouses and factories to Scotland, and you create considerable extra costs and delays, which is why they're busy building a huge lorry park in Kent
The true scale of a massive post-Brexit lorry park has been revealed in a series of drone photos as contractors start to work through the night.
www.kentonline.co.uk
That's not a problem because of any history between England and France, it's a problem because of the need for customs checks.
It's exactly the same problem, as I see it, as we had with the EU referendum.
At the time I said it was a nonsensical idea because we were being asked to choose between the status quo and something else, without being told what the "something else" was, and whenever people like me raised questions about the practicalities, people like Michael Gove and Boris Johnson dismissed our concerns as "Project Fear" and told us that we would enjoy all of the advantages of belonging to the EU without any of the disadvantages.
As we know only too well, that assessment of what leaving meant turned out to be somewhat over-optimistic, and one of the disadvantages of creating a border between the EU's single market and the UK is that you thus create the need for customs checks and controls, and lots of paperwork.
If an independent Scotland joins the EU, then it creates a similar border between Scotland and the remainder of the UK, where no such barrier exists at present. Similarly, it decouples Scotland's banking and financial services market (which accounts for a huge proportion of Scotland's GDP, up there with oil, whisky and tourism) from London and UK regulators and places it under EU regulation. That has to cause significant disruption to the industry on both sides of the border.
As I said in an earlier post, the only way I can see it working is if Scotland and the rest of the UK apply to (re)join the EU at the same time as Scotland gains independence from the UK.
Furthermore, at some point before the referendum, someone needs to consider what happens if Scotland's application to join the EU is unsuccessful -- Spain vetoes it because they don't want to give the Catalans ideas, or Hungary and Poland veto it because they think the Scots are too liberal, or Marine le Pen becomes President of France and vetoes it because she's a fascist jerk.
Probably wouldn't happen, but there has to be a contingency plan -- does Scotland still want to be independent under those conditions, and, if not, where does that leave the referendum result?
The more I think about it, the more improbable it all seems.
