At a high rotation rate, the silicon sections will stretch due to the mass of the "ring". 

High speed flywheels are made of carbon composite to keep the mass low and the strength high.  the forces on the "ring" will be huge.  Mass has a slight effect on the energy stored in the flywheel, but the velocity has a huge effect, so it is better to use a light, strong material and spin the hell out of it.

Here is the equation which shows how the mass and velocity relate to energy stored in the ring (wheel):

 

Allows it to conserve itself?  How does this arrangement allow that?

Add all the mass you want and the damn thing will blow apart.  Tesla had the same problem with his turbines.  Material was too weak to take the forces created by the high velocity and the discs would stretch.

Also, why make a multipole ring when you can rotate a multipole field much easier - without the shrapnel.

 

If it spins around a center point, it has a center of rotation and it has a center of mass.

What you are talking about is a called a "centerless flywheel" - been around since the 70's - maybe even earlier.  Howard Blake wrote a paper on them back around 1975 - used composite materials.

You might think that the magnetic field is strong enough to hold it together and maybe it is at low rpms.  There are already flywheel systems with magnetic bearings that spin up to 100,000 rpm - 90% efficient - no OU.  Some of these are built with magnets on the rotor, counter rotating rotors - all sort of stuff.

PS - Any conductive material within the rotating magnetic field will be heated by induction.

PS2 - You will store more energy with speed than you ever will with mass.

PS3 - You can rotate a multipole field, without the mass, without the bearings.