"Nobody's defined what'll make Scottish nationality"

That isn't true Guest. The Scottish gvt have given their proposed definition in chapter 7 of their white paper.

Some people will automatically qualify as Scottish citizens. For instance British Citizens who are habitually resident in Scotland including those with dual or multiple nationalities; and Scottish born British Citizens currently living outside of Scotland.

Others will be able to apply for citizenship. For instance through descent from a parent or grand-parent; those who have a demonstrable link to Scotland; or migrants on qualifyiing visas.

Of course the exact rules wouldn't be laid down unless it actually happened. It isn't for one party to dictate what would be - it would be for the Scottish Parliament to agree it as a whole. But it is simply wrong to suggest no-one has defined it or addressed the issue.