You've mentioned two important factors but the harder standards to be met are economic. This[1] covers it quite thoroughly, is written by someone I would expect is in favour of joining the EU (though I'm not sure) but I think they've done a fair job, and some (some) of the comments too.

Once those are met then thorny issues like a hundred mile long border can be looked at. I don't think it's impossible, but, as is covered in the first link (and many other places, did you look?) Scotland cannot swan in to the EU in less than 2 years even at the very best. And without the Euro?[2]

[1] https://sceptical.scot/2020/03/can-scotland-meet-eu-economic...

[2] https://www.channel4.com/news/factcheck/factcheck-independen...