Lex, see my post about multi language here (https://forum.mendix.com/link/questions/5419 ).
Create a new entity for the translatable string (you could use the enumeration and the getcaption to fill these objects). Since this object has a reference with language you can use this to show the object twice each with a different xpath based on the different language.
This way new languages can be added easily.
Can be achieved in different ways, add the 2 languages in the app. And then add the caption values per language by toggling the language in the top bar.
Then set the caption enums with double values.
flemish value / (french counterpart)
french value / (flemish counterpart)
Or you could instead use a reference selection of an entity containing both values. And display this referenced entity next to the reference selector and display the french translation next to the dropdown.