What if somewhere after WWI (maybe after result of Trianon Threaty) Hungary and Romania agree or has been forced to exchange the popluation in such way: the Hungarians and Szeklers would be deported to Northern-Western teritories of OTL Romania (Oradea, Bihor, Salay, Satu Mare, Baia Mare) and the Romanians from those theritories would take areas left by the Hungarians and Szeklers.
Similar thing could be done in Yugoslavia with north Banat
Why Entente would want such thing? Let's assume that in the next war Entente want to have Hungary with lesser grunge against Trianon.
In the WWI Serbia and Romania were mostly beaten by AH than attacking .
The PODs would require stronger Hungary, without self-disarment (or on lesser scale).
Could such scenario with federalisation of Czechoslovakia (with Hungarian autonomous area) and better Hungarian - Czechoslovak relations hold Hungary back from military cooperation with Hitler?