What is Nationality theory? Well, urm... you know what Nationality is, right? Sure you do, you're not stupid. So there's bound to be some particularly silly way of talking about it such that paradoxical results are generated and suddenly you aren't so sure but, because you definitely aren't stupid, you just keep keep saying more and more stupid things till your gibberish qualifies as a full fledged Nationality theory.
The amount of harm this can do rises exponentially once you try to fit this Nationality theory into the existing pragmatics of the State. So obviously that's the next thing on your to-do list.
A methodologically individualistic approach, building on insights from Aristotle through Aquinas to Leibnitz, might yield something like this-
Thus, the Ottoman State- with more or less autonomous Millats (Nationalities/ Sects)- could have had 'Golden path' Freedom if it had been configured to prevent or bounce quickly back from ethnic strife. It has been argued that its imperfect de-feudalization and Corrupt or Sectarian resistance to 'Tanzimat' reforms, put paid to its hope of 'Golden path' Freedom-as-coexistence and that, in any case, the 'Balance of Power' concept of the Concert of Europe was bound to instrumentalize divisive Nationalism within its territories as part of its own biased ergodics.
Something similar would be true of any multi-national State under a 'Balance of Power' equilibrium. Each would have an incentive to instrumentalize divisive Nationalism- albeit, perhaps, through the proxy of 'Class'(some Nationalities might be seen to be 'essentially' more working or middle class) or Gender (some Nationalities might be seen as essentially more or less sexist) or the Environment (tribals are nice to the Environment whereas other people who look exactly like them and live in the same place are very evil)- outside its own borders precisely because of a similar buffeting it, itself, receives as part of a wider Brownian Motion. Divergence of Economic interests within a Nation- as between Bond Holders, represented, in England in the Twenties, by the Times and Morning Chronicle, and Manufacturers, whose mouthpiece was the Manchester Guardian- too, might militate to the same end.
The problem here is that signals emanating from the ergodics of the Equilibrium between States interfere or contribute noise to signals from the Economic Optimal Migration Theory such that pathologies can develop though the appearance of 'free movement' obtains.
What is the free market solution?
Essentially, a signal extraction problem is going to change the Schelling focal points for markets such that 'buffered' local Tiebout models, yielding untaxable Manorial rents, gain salience in a manner that weakens the State for weal or woe.
From the Ideological point of view, it is impossible for us to know whether we inhabit a Tiebout or a Universal model and so, in so far as we blog about Optimal Migration & Nationality theory, we just add noise to the signal to create a confusion worse confounded.
So, no change there then.