They are unusual, because they respond to highly unusual circumstances. They imply risks that have to be carefully weighed and mitigated. But fundamentally, unconventional tools are only a means for central banks to continue doing what they have always done: managing aggregate demand, by influencing the level of real interest rates and other monetary transmission channels, to maintain price stability.
This framework may become a standard for enterprise risk management similar to the way the COSO Internal Control Framework has become the benchmark in its area.