Hi Utnik,
Thanks for your reply!
The point is not so much that I need to edit in InDesign on a regular base. As I recently started as a self-employed designer I use Gimp/Scribus/Inkscape/Blender. My customer, however, wants a back-up plan in case something happens to me, so they can retrieve the data in an editable way. So hopefully it is something I am not going to use

but I want it to be in place. From what I understand ID can import PDF although it might require a commercial plugin.
When I export to PDF, the vector structure remains. When I open it e.g. in Inkscape, I still can edit the different elements. Of course typical Scribus elements like guides and so are gone, but at least the basic data is there.
So for me this would be a viable option, if the text frames would remain intact. But as it seems now this is not possible, unless there is some kind of work around or so.
FYI: I managed to embed Arial Regular in a PDF on an Ubuntu machine. You only have to unselect subset in the Fonts Preview. On windows 8 (not sure about other Window versions) you can uncheck it and the font can be put in the embed section, however, in the resulting PDF the glyphs are still vectorized. But may the FontForge offers a solution here.