Travelling with 2 national ID(s) [duplicate]

In general this should be possible.

Some countries might have restrictions on the use of ID cards. For example, the US passport card is for use as a travel document only for land and sea travel to Canada, Mexico, or the Caribbean. Such a country might not permit its citizens to use the ID card when arriving from certain countries.

But most countries recognize an obligation to admit their own citizens, so the adverse consequences of violating such a restriction, if any, probably won't include denial of entry.

One must also convince the airline to allow travel with the card. Airlines use a database called TIMATIC to check these requirements. TIMATIC notes that both Belgian and UAE citizens can enter with an ID card, so in this case it should be possible.

The US seems to have a somewhat problematic and poorly documented requirement that departing passengers be in possession of a passport. Any country that has such a requirement might pose a problem to such a traveler, but I recall reading a report here about a European who managed to fly to Europe from the US with her ID card, after some discussion with the airline's ground staff.

As an aside, a Belgian can also avoid stamps from EU and Schengen countries by presenting the Belgian passport.