[usrusr]

But here that mass is the driving force: the further away from the center you put your magnets, the less force (the less magnet) you need for a given amount of Newtonmeters. When you move that mass away from the center, you need less mass, changing at the same factor as rotational inertia changes. So no improvement or drawback in terms of rotational inertia, but improvement in terms of total mass (and improvement in terms of unsprung mass when comparing to a wheel motor in the hub).

In a way this is a transfer of semiconductor miniaturization to motors: when your power transistors can switch fast enough, you can replace fewer bigger coils with more smaller coils (that switch more often per rotation) and moving it all rimward gives you more torque per Newton. That ice skater effect? It's on your side.