paull
If someone lets us know at what mass these bits are nolonger a danger to the wing then "all" you have to do is design in a weakness for controlled (but more frequent) failure and you have "Containment". Unfortunately there are also an infinite number of these things so at the end of the day it probably just comes back to an energy calculation unless you can get it to fall apart slowly, spreading the energy release.
Yup, you have an understanding of this. The regulation addresses this on the basis that three equal size infinite energy segments are released simultaneously. The regulation also considers lesser size fragments but historically only one of these is expected to have infinite energy.
Unfortunately designing dotted lines on spinning parts to assist them breaking into small bits adversely affects how often they break and go boom in the night.