Well, it's un-inhabited, so it's a lot easier to swap, as opposed to exclaves who usually have inhabitants who would not be too happy to switch nationality.
Dahala Khagrabari is a piece of India, surrounded by Bangladesh, surreounded by India, surrounded by Bangladesh.
And things stay this way because it is quite awkward to change places where people live to belong to another nation - however impractical these exclaves may be.
Dahala Khagrabari is no longer an exclave. India and Bangaldesh executed a wide-ranging land swap in 2015 to resolve a large number of these tiny exclaves.
Scroll a bit further north, and you will find a single, small German farm just inside the Belgian border. Apparently it's abandoned because the occupant got sick of trying to convince the German authorities that his land actually was in Germany when he needed this or that.
The thorniest question seems, to me, to be how to integrate local government on the city or county scale. Citizenship is fairly straightforward - make the inhabitants citizens of both countries, and let them renounce one and live in the other if they wish. How to ensure that a village has the zoning regulations they want when it was handled by a county in another country seems trickier.
The Netherlands do not allow dual citizenship, so simply allowing all the Belgians/Dutch to chose during an Enclave/Exclave swap wouldn't be possible.
It wouldn't be necessary really, as citizenship is more dependent on your parents. Both of them being EU member states also makes residence somewhat irrelevant too, except maybe with taxes.
Yes, parent should have written "country they live in" rather than nationality. But the basic point holds of course.
Lots of people would be unhappy to suddenly live in a country where they're not a citizen and subject different laws, taxes, and health care. In fact, it's not hard to see why it would be pretty much a non-starter politically.
pretty sure that the residents of baarle hertog quite like the status quo. If one country does something they don't like (e.g. tax policy), they can redesignate their "front door" as being in the other state, and thus be under the other state's jurisdiction.
