Possible to have a single entry page with multilingual slugs and only one index.html?
What you're asking for is fine. Create a subfolder within your public directory for each locale with it's own index.php and define the new path to craft/ and the locale. For example, within public_html/fr/index.php you might have:

// Path to your craft/ folder
$craftPath = '../../craft';

// Tell Craft to serve the FRENCH content
define('CRAFT_LOCALE', 'fr');


With the single, you set the slug yourself within the section's settings (one slug for each locale that section is available to).