The latest version (V2) is now assembled and tested. Some improvements are still possible, but for now I am happy with the results. Video has been recorded with the battery almost empty, normally it has mouch more power!
For future upgrades, I will design and 3d print some adaptors so the DIYson can also work as a leaf blower, and maybe other functions too. I also plan to add post motor Hepa filter, the top part has a thread so I can easily add it later.