Preferred language option

I would like to add another language selection mode, which I called "preferred".

Here is how selection behaves:
- if the node has no language, display it
- if the node is available in current language, display it
- or else, if the node is available in default language, display it
- otherwise, don't display it
I hacked i18n.module to do so. The number of changes is quite limited:

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>  *      preferred = Current language or else (if available) default language, and no language
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>     'preferred' => t('Current language or else (if available) default language, and no language'),
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<       
<       $result['join'] = "LEFT JOIN {i18n_node} i18n ON $primary_table.nid = i18n.nid";
---
>       if ($mode == 'preferred') {
>         $result['join'] = "LEFT JOIN {i18n_node} i18n ON $primary_table.nid = i18n.nid LEFT JOIN {i18n_node} i18n2 ON i18n.trid = i18n2.trid and i18n2.language = '".i18n_get_lang()."'";
>       }
>       else {
>         $result['join'] = "LEFT JOIN {i18n_node} i18n ON $primary_table.nid = i18n.nid";
>       }
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>     case 'preferred':
>       if ($alias == "i18n"){
>         return "$alias.nid IS NULL OR $alias.language ='".i18n_get_lang()."' OR ($alias.language ='".i18n_default_language()."' AND $alias"."2.nid IS NULL)" ;
>       }
>       else {
>         return "$alias.language ='".i18n_get_lang()."' OR $alias.language ='".i18n_default_language()."' OR $alias.language ='' OR $alias.language IS NULL" ;
>       }

Do you think that such a hack is OK?

I am quite concerned by the SQL request. I am not a specialist and don't know how heavy it can be on a large site.

Thanks for your comments.

-- Denis.