Personally, I avoid multisite unless it is really necessary. It has several quirks I’d just as soon avoid where possible. I don’t think it’s necessary in the case you describe. For one, there are several multilingual plugins you could implement on a single WP installation.
You might not even need a plugin. While certain pages are intended for only a specific language, there is no problem with others accessing it if they were so inclined, correct? You could introduce a language permalink element by creating pages as children of an overall language page. For example, create a page whose slug is “de”. The content is unimportant, it could be a list of German language pages. Create another page with “de” as parent, say “shop” or “geschaft”. The shop page’s permalink will then be something like example.com/de/shop/. You can do similarly for other languages, or don’t use a language parent for the pages in the default language.
If by chance you need additional access control, it can likely be accomplished with a membership type of plugin or some custom coding. I don’t see multisite being necessary, given the information you’ve presented.
