Since Hermann's hermetica are permanently removed from his character sheet when he uses them I think they should be treated as disposable equipment. That is, yes, he can fill that slot with other equipment after using the hermetica.
The new FFG home page confuses me. I can't find the release dates for upcoming games. There used to be a page which said what games were "on the shelves" or "shipping now" and so on. Is that page gone?