One problem with this system concerns the representation of citizens who reside abroad. Insofar as such persons remain citizens of the country in question—the state remains the ultimate protector of such citizens’ rights and interests; it is the one place that they can go to if denied residency elsewhere—it would seem that they should have some kind of representation in their country’s legislature.
Many countries allow non-resident citizens to continue to vote within the electoral districts wherein they last resided, at least for a certain period of time (currently, Canadians can vote in federal elections so long as they have not resided abroad for more than five years). But a better form of representation, I think, would be to allocate a certain number of MPs to represent directly non-resident citizens.
Or so I have proposed in the past—viz., that there should be a number of MPs within the Canadian federal Parliament to represent Canadians abroad. (Such forms of representation, it should be noted, already exist for French and Italian citizens.) Interesting, a Briton residing in Spain recently has made a very similar proposal, and has started a petition to get the proposal debated within the UK Parliament. I wish him luck!