This is a really hard question to answer because how you ask it is almost always, unavoidably, going to make assumptions about what nationality is.
Historically, the ambiguity in the term 'nationality' stems from it having two meanings, with most people using the term to mean something in between the two extremes:
The first conception would have 'nationality' entirely synonymous with 'citizenship', in which case it would change with borders. This definition makes no distinction between 'nation' and 'state'. In that sense, it's a limited definition of nationality if you wanted to make sense of, say, the refugee crisis in Europe during WWII, where the nation/state distinction is central to understanding the events that take place and what follows (e.g. the 1961 UN Convention on the Reduction of Statelessness).
The second conception has 'nationality' as a kind of ethno-lingual-cultural construct, your nationality is the 'people' to whom you belong. While this might seem in some way outdated to some people, many countries still offer almost unconditional citizenship to foreigners who ethnically originate from the country. A well-known example of this, although a slightly unorthodox one, would be Israel's 'right of return', granted to all Jewish people. This conception of nationality is closely aligned with early 20th century nationalism (think about the kinds of assumptions behind a map like this).
Personally, I'd say the biggest problem with the view your espousing is what happens in cases like your example, where someone's 'nationality' is, according to your conception, aligned with a state that does not claim to represent or protect them, or even a state that doesn't exist any more. Legally, this is a really difficult situation: if I'm Romani (gypsy) and a Romani nation is formed, how will they grant citizenship? Surely they would need something similar to Israel's 'right of return', but that relies on a much more nuanced conception of nationality than one that simply refers to the political boundaries one was born inside.
