Hey Dan,
glad you like the Kunstmaan Bundles CMS! We put a lot of hard work in it and are always glad if people discover and use it. If your website goes online, please submit it for the showcase gallery.
Now in regards to the translations on page level you mentioned, this was actually an explicit design decision. We've been building loads of sites in a multilingual environment (NL/FR/DE/EN are the most common but recently we also launced a chinese translation for a site) and more often than not does the content of a page (apart from the literal translation) differs between languages. The message is often targetted differently to different languages.
It's a lot easier to do this with page level translations than pagepart level translations. It also makes it possible to do user-understandable versioning, what page with what content was online at that point in time.
As you mentioned you can indeed solve a lot by just creating custom pageparts. Apart from this we also provide a "copy from locale" option to copy all content and pageparts from an existing language to untranslated languages. This does however only solve the initial data input for this page. A screenshot of this feature
Regards, Roderik