I'm just saying that the concerns are separate: a block provides generators, transformers, serializers, ... to other blocks, but those are de-coupled from the real java components (if any) doing the job.
But *real* blocks, IIUC, *are* the only way to bring new (java) components into the system, because Cocoon core lacks all the optional components, and, at the minimum, consists only of environment, treeprocessor, and block manager.
So in extreme case xslt processor component itself is optional and provided by the xslt real block.
Vadim
