I fear you are too optimistic. In the event of a "yes" vote Scotland will be jettisoning itself from the EU on the date of its independence -- no one else will need to jettison it. So the EU will be contracting. There's already a precedent for this, in Algeria, which did not retain its EEC membership when it left France. I'm quite sure that Scotland will be able to rejoin the EU, and probably even jump the queue a bit, but it's extremely uncertain that it will be able to keep the UK's opt-outs, which will require unanimous consent from all 28 existing members.