The more I read about the recognition that an uncontained engine failure including a disc breaking up (ie not just shedding blades) is a recognised possibility, the more surprised I am that every engine does not have failsafe 100% automatic 100% mechanical mechanisms to prevent an overspeed. Surely it is possible to insert a brake which is triggered automatically as soon as a turbine starts to overspeed, and to also include a fuel cut-off, and possibly movable guide vanes to neutralise torque generated by the hot gas.