TBH - when Scotland IS independent who will be the threat?
Russia? - too big to take on - ignore or adopt a policy like Finland 1945-1990
Ireland, Norway, Denmark, Iceland, Faeroes - ridiculous - fishing wars only
England & Wales - possible but unlikely
The rest of the EU - no
So if they are independent and they ditch the hang-over of Empire they are a small country on the edge of Europe who are unlikely to be threatened by anyone - so they need a cheap MPA, some fisheries protection vessels and a small Army for internal security