I found this part to be particularly interesting. It is evidence that, as Aubrey de Grey has long maintained, somatic nuclear DNA mutations are not important, as long as they don't lead to cancer. The caveat is the possibility that this woman had particularly good DNA repair or apoptosis mechanisms. The same deep sequencing study needs to be performed on more people of various ages in order to nail this down.
Holstege says the other remarkable finding was that the mutations within the blood cells were harmless all resulted from mistaken replication of DNA during van Andel-Schipper's life as the "mother" blood stem cells multiplied to provide clones from which blood was repeatedly replenished.
She says this is the first time patterns of lifetime "somatic" mutations have been studied in such an old and such a healthy person. The absence of mutations posing dangers of disease and cancer suggest that van Andel-Schipper had a superior system for repairing or aborting cells with dangerous mutations.
As for the idea of banking youthful stem cells, that might work for some tissues (e.g. blood) but not others, like brain. Given what we now know about reprogramming of somatic cells to induce stemness, it should be feasible to select healthy cells, or to rejuvenate either stem or somatic cells, and grow crops of healthy stem cells to replenish waning stem cell pools.