Scotland currently meets most EU criteria for membership, already complying with EU laws and regulations. The mood from Brussels is very different to that of 2014 - when Scotland voted on leaving an EU state, the main message being that if a Scottish independence referendum is legally and constitutionally valid then Scotland is set for a reasonably swift accession process. For the EFTA states such as Finland the process only took 2 years. The only real problem could be currency - the Scots think they could continue to use Sterling for a time after independence, this is denied south of the border. However this problem can be got around - there are several countries which use the US dollar without asking for the American's permission to do so. The main thing is that an independent Scotland would satisfy the democratic conditions for joining the EU - actually England (the remainder of the UK) could have problems trying to rejoin for this reason - attacks on the independence of the judiciary definitely don't go down well under EU laws. I am sure that if the will is there on both sides then Scotland will have a relatively smooth transition into the EU - just think, a future Scotland could veto prospective deals between England (what's left after Brexit) and the EU