The only other way that you could measure a disks stored energy would be to measure the work required to accelerate the disk to a fixed velocity over a fixed time. Havent thought this through yet, but once a formula is thought out and equipment set up, measuring a new disk would simply be like balancing a wheel.

Not saying its easier, but should be more accurate, and require only the initial effort as opposed to having to take each disk from scratch, and as you say calculating each change of shape/part as you would have to. This may be easier for one or two, but over time still being laborious.

Dont have all the answers.
Roger