Do you have a link or could you explain more about the actual hygiene requirements? I remember reading the linked article at the time and the challenge of keeping cells bacteria free did sound pretty daunting.
Just testing the viability of that one sentence would be a decade long research project for a large, well funded lab - and it would definitely not work as described.
Cell culture is hard, immune systems are incredibly complex. Bone marrow cells are very hard to culture, relative to other cells - we literally figured out how last year, just about, for one of the cell types in bone marrow niches. The collection of complex cell types in bone marrow and are only one component in a functional immune system.