For those interested, I've open-sourced my localization code generator here :

https://github.com/senselogic/LINGUI

It converts human-readable translation scripts into compilable D/C# code.

For instance, this script :

    Game
        New_game
        Welcome first_name last_name
        Pears count

    English : Game
        New_game
            "New game"

        Welcome first_name last_name
            "Welcome, "
            first_name
            " "
            last_name
            "!"

        Pears count
            *count
            " "
            if @count = one
                "pear"
            else
                "pears"

    German : Game
        New_game
            "Neues Spiel"

        Welcome first_name last_name
            "Willkommen, "
            first_name
            " "
            last_name
            "!"

        Pears count
            *count
            " "
            if @count = one
                "Birne"
            else
                "Birnen"

    French : Game
        New_game
            "Nouveau jeu"

        Welcome first_name last_name
            "Bienvenue, "
            first_name
            " "
            last_name
            " !"

        Pears count
            *count
            " "
            if @count = one
                "poire"
            else
                "poires"

Can be used this way :

    // -- IMPORTS

    import std.stdio : writeln;
    import ENGLISH_LANGUAGE_MODULE;
    import FRENCH_LANGUAGE_MODULE;
    import GAME_LANGUAGE_MODULE;
    import GERMAN_LANGUAGE_MODULE;
    import TRANSLATION_MODULE;

    // -- FUNCTIONS

    void Test(
        GAME_LANGUAGE game_language
        )
    {
        writeln( game_language.New_game() );
        writeln( game_language.Welcome( TRANSLATION( "Jack" ), TRANSLATION( "Sparrow" ) ) );
        writeln( game_language.Pears( TRANSLATION( 0 ) ) );
        writeln( game_language.Pears( TRANSLATION( 1 ) ) );
        writeln( game_language.Pears( TRANSLATION( 2 ) ) );
    }

    // ~~

    void main(
        string[] argument_array
        )
    {
        Test( new ENGLISH_LANGUAGE() );
        Test( new GERMAN_LANGUAGE() );
        Test( new FRENCH_LANGUAGE() );
    }

Which will thus print :

    New game
    Welcome, Jack Sparrow!
    0 pears
    1 pear
    2 pears
    Neues Spiel
    Willkommen, Jack Sparrow!
    0 Birnen
    1 Birne
    2 Birnen
    Nouveau jeu
    Bienvenue, Jack Sparrow !
    0 poire
    1 poire
    2 poires

I know there are other ways to do this, but for Unity games this was what best matched my needs, especially performance-wise...

Nice job!