I think that if you make the annuli of the 8 gear sets the MGU-K and each is capable of different RPM and torque, you would be using 8 MGU-ks and you are only allowed one. Plus it must transfer energy only to the engine, engine ancillaries or other ancillaries. I would think that if it could apply directly to the gearbox, it would have to show it in the diagram at the bottom of the regulations.
In order for it to be legal, I think the gearbox motors would need to be separate from the Battery pack and fall under the other energy storage allowance. Apparenty the driver does not need to control the gear changes directly, but there must be only one gear change per shift by the driver, and some other control strategy restrictions, but I think your system is able to comply to those rules.