I spent some time thinking how to make the building process as easy as possible, after all the motor needs to be printed, colied, assembled, mounted and controlled. The first concept wasn't very user friendly in that sense.
Fig. 1: New concept. Looks like a standard stepper motor.
This second concept is all about using off-the-shelf parts. It's controlled like a 2-phase stepper motor when the rotor has magnets on it (synchronous) and when coils are put on the rotor it works as an asynchronous motor.
This makes it easier to control, stepper controllers are really cheap these days and I happen to have some at hand so I won't have to build custom electronics.
For the rotor it's probably better to use something sturdier than a printed axle, a metal rod will do. I decided to use the tiny 635 type ball bearings on either side of the rotor as well. The motor can still be made with only printed parts though.
This is still a concept, I haven't printed anything yet because I don't have access to my printer currently.