But they aren't capable.

Real politik.

They would need a currency. The UK chancellor has said he cannot allow sharing unless this was in the interest of The UK, which is correct. Therefore, if Scotland wants to use sterling, they would be bound to UK interest rates and international exchange rates influenced by UK policy.

Doesn't sound like independence to me.

If they wanted to join The EU, they would , as every new member has to, use The Euro. Again, fiscal policy set abroad.

A long term future based on short term oil at a price set by OPEC in a currency exchange set by London or Frankfurt? Might work if you shoot your pensioners.