The "OSCA" concept should be more of a federated collection of books instead of a centrally managed resource. This will enable greater contributions from the Bioconductor community, rather than being restricted to a handful of maintainers. Most importantly, books can be contributed by the same developers who maintain the package(s) used by the book. This avoids a major problem in book maintenance whereby package updates cause unexpected changes to the results in the book.
The flipside of many separate books is that a greater burden is placed on the reader to assemble the disparate bits of knowledge into a functional workflow.