I don't really know enough about the subject at hand, but even though it seems like a logical exchange of territory for a permanent exchange, the Fascists seemed to want to hold the Dodecanese as a staging area against Greece in future. However, if we use the interwar period pre-Mussolini, I guess you could have a situation whereby the Ionian islands are seen as more valuable due to their position at the southern end of the Adriatic, thus being able to hem in Yugoslav shipping. Regardless of who comes to power, the Italian interwar government is most likely going to be actively opposing the status quo under the vittoria mutilata.