I don't know how many of y'all are outdoorsmen, but the shimano company has been applying this principal to fishing reels for years to adjust reel speed when casting. They have six pins on the end of the spool the radiate outward, each pin holding a weight that snaps to an up or down position, moving mass as needed.
Having a machine trade background, I could see where individual precision weights could be bolted symetrically into and out of pockets machined in a flywheel to tune mass. They'd just have to be very close tolerance and added absolutely symetrical. Large rotating equipment in powerplants and chemical plants are field balanced with bolt in weight all the time. The idea isn't that far fetched.
Jet engine fans are balanced the same way...
I could see there being some application for this type of thing for the high dollar drag racing folks. Us mortal street drivers... prolly not as much. hehe
hmmm
I'll think about it and maybe email you a print.