Interesting thoughts on the Border. The comparison with Ireland is interesting. One of the reasons the UK/EU opted for the Irish Sea rather than the land border is because the Island of Ireland was and will continue to be treated as a single regulatory zone for agriculture.
The Art 16 debacle has highlighted that this is envisaged to apply more widely to infection control and food and drug regulation going forward. If we had Covid in a couple of years time the UK could have been in the position of having to negotiate with the EU to supply vaccine to its citizens in NI because the EMA had not authorised the vaccine and the UK had. I suspect there will be some nuancing of this across the Border now. The first play is the UK offering to supply Ireland as a priority once we have any spare (Liz Truss on Marr this morning).
Re-imagining Scotland and England as separate regulatory zones looks like a complete non-starter and to do otherwise would make Scotland joining the EU near impossible.
Not so concerned about freight as Scotland uses airfreight more than you would think and the cost difference is not huge (similar to me having very little use for the Channel Tunnel if I want a weekend in Paris). Most whisky is by air.
More concerned about food security but again having lived in London and Scotland (with family all over the South East) it is very noticeable that supermarkets have completely different produce supply chains. Scotland is not really reliant on cross channel supply at all but sometimes if its on a lorry anyway it makes sense to share with England. (I went through a phase of checking every time I went to Sainsburys post Brexit and the DC are now on first name terms with all the Fife fruit growers).
Agree on the Freedom of Movement Issues. Everyone is politely pretending the special CTA arrangements for Ireland don't have the potential to act as a UK backdoor but they do and adding Scotland may well be incendiary.