They'll do what Ireland did. Leave it up to the warlike English to defend them. Which is kind of amusing, since a big reason England conquered Wales, Ireland and Scotland was to put an end to raids into English territory.
“warlike”? Is that like ‘safety net’?
It's cynical as heck, but any state that seceded from the union would probably do something similar, assuming secession occurred peacefully. The only way for England to guarantee that an independent Scotland maintains a strong defense is to attack and bomb the heck out of it, and generally work to prevent it from leaving the union.
England never conquered Scotland. In fact, the Scots ultimately repelled invasions by the Romans, Danes, Vikings, Angles, Saxons and Normans, as well as the English. One hell of a record. Amazing. There’s an old Scots saying: ‘occupied many times, but never conquered’.
The Union of 1707 happened because Scotland remained an independent country.