RotationalInertiaFactor is available in base_ship which is great but there are a number of cases where having a component to change a ship's RotationalInertia is desired.
For example:
- the wing parts I've suggested before. Without, this would require buffs that can be a rampant problem if used with area effect or extremely complicated with precise control and (more than) half a dozen buffs.
- similarly related parts have the same requirement and would end up using similar systems.
- It would make the often suggested rotation gyroscopes / inertia manipulation devices possible; preferable as part of vanilla, though.
Having a component that directly changes a ship's rotation capability would avoid a lot of the complexity and lag.
However, there's a problem if used it similar to buffs by using a percentage change. Changing based on percentage would quickly make any ship OP. So I suggest to use a mass based calculation. For example a gyroscope would give a reduction of 10 tonnes to the total ship's mass in the calculation for RotationalInertia. Unless the game doesn't use mass in the calculation to begin with. This would be a problem in realizing it.