One way is to just write a PERFORM method
(defmethod perform ((o doc-op) (c (eql (find-system :my-system)))) (operate 'load-op :foodoc) (funcall (intern "DOCUMENT-SYSTEM" :foodoc) :my-system))
However, regardless of details of how people are expected to write those ops, I think exporting a DOC-OP is uncontroversial, so I've confirmed this.
One way is to just write a PERFORM method
(defmethod perform ((o doc-op) (c (eql (find-system :my-system))))
(operate 'load-op :foodoc)
(funcall (intern "DOCUMENT-SYSTEM" :foodoc) :my-system))
However, regardless of details of how people are expected to write those ops, I think exporting a DOC-OP is uncontroversial, so I've confirmed this.