It seems like it would be relatively straightforward to make an sqlite based file format and just have users add a plugin if for some reason they couldn't upgrade their older version of LibreOffice etc. I agree with the other commenter who mentioned that the benefits for text and spreadsheet files needs more explanation. But it seems like a good enough idea to have a LibreOffice working group perform a more in depth study. If significant memory reduction is real and that would translate to fewer crashes, it would be a huge boost even if it had no other benefits, IMHO.