You cannot become scottish. You can become one of the people of Scotland / a Scottish resident.
This makes me a bit uncomfortable. It’s like saying to, for example an Indian immigrant ‘You can live here, work, pay taxes, but you will never be British, always less than one of us.
I’ve lived in Scotland more than half my life, I actively chose the place, commited to it, and contribute to society through work, taxation and in many other ways.
I see myself as more Scottish than Sean Connery, who would do anything for Scotland but live there, and is just Scottish by virtue of an accident of birth.