I don’t think the challenges to Scotland rejoining the EU are insurmountable. But in no particular order of importance.
1. Scotland’s Gov spend is “roughly” 61% of GDP and growing. The EU admission rules are no more then 60%. that means cuts somewhere.
2. The Euro. SNP say they’ll continue to use Sterling. I cannot, under any circumstances, see the EU agreeing to it’s use at all, especially the currency that the member state doesn’t control, and is the currency of a member state that’s recently left the union.
3. The need for a hard border across it’s biggest trading partner. We know now that the EU will not negotiate on this
None of these are insignificant.