As already mentioned, I have designed a spool holder which holds the spool above the build plate. The filament just runs straight down: no tanglement possible.
See the link that was posted. I just edited the description, added two pictures of the final (?) V3 version and removed the „Work in Progress“ mark.
It will not fit in the upcoming enclosure, though 
I will see how the filament runs in the enclosure, and if I‘m not satified, i will see if I can design something there. Maybe even take another plate of acrylic glass for the top and cut a square for my holder and a slit for the filament…