Multilingual work material setup

Dear all,

I am venturing into a multi-lingual work. Each version of the book will have two languages side-by-side, for example the first version will be German (original) and French (original translation), and the second will be English and Italian. 

While the setup of the InDesign document is straightforward in my mind (one layer per language, or couple of languages), one frame per language to allow proper reflowing, I am still in a previous phase. What I'm doing now is gathering/copying all the original German and French material to then have them be corrected and proofread by native speakers before any translation to English, Italian, and more will be possible.

As much as I have worked in page layout, I am extremely dissatisfied with my current workflow and I'm looking for advice: I am using Apple Pages, but could use Microsoft Word, but creating multi-column docs there will make my life harder at the end when the DOC needs to be imported in InDesign. The lesser evil, for now, seems to have a separate document per language and having them open side by side onscreen. 

What do you think?

Any better idea?

Perhaps already start in InDesign with each page bearing two frames, one per language? Or a spread with four total frames, one per language? Or something else? Perhaps then using InCopy for faster input? 

Thank you!