including only "teacher data" could be very problematic as some modules, forums, for example, have such data (posts) mixed with "user data" (other posts). Trying to backup/restore only teacher posts would break the structure (because missing student data creates "holes" in the discussion tree).
An alternative to activities requiring initial teacher data is to implement some type of "virtual teacher" in the backup file. Such "virtual teacher" will be associated to an existing teacher at destination (if it exists) or will ask for one, or something similar...
Ciao