It should be possible to provide a revision_id to the Segmenter to return the segmented version to that revision of the page.
The minimum implementation is that the revision_id is used to look for a segmented version of that revision in the cache (i.e. if it was segmented when the revision was the latest one). If not found it can simply return an error saying the revision is too old.
A more fully fledged implementation later would allow segmentation of historical revisions.
In either case the Segmenter must check if the requested revision is still accessible (in case of RevDel).