David's Ring Extruder

This is just an idea, and needs lots of thought. Don't print it out as it stands, it's really just posted to stimulate thought. Basically working on the principle that the more surface area contacting the filament the better, I haven't found a handy bit of pipe (probably 50mm stainless would work OK), and my Sanginolulu died, so waiting for a fix.
There are lots of flaws to the current design such as:-
-likely needing extra bearings to support the rings.
-probably motor drive would be bet