In one of my projects I have a separate field 'langs' that editors can check. Definition (for RockMigrations):
'langs' => [
'label' => 'Languages',
'tags' => 'general',
'flags' => 0,
'type' => 'FieldtypePage',
'derefAsPage' => 0,
'inputfield' => 'InputfieldCheckboxes',
'parent_id' => '',
'labelFieldName' => 'title',
'optionColumns' => 1,
'template_id' => 'language',
],
So it is a page reference field that gives you checkboxes for each language.
You could then use the value of this field in your logic for the language switch.