Erk, I forgot two items.
QA - This one is a strange one. SOME of this would be in the documentation layer; some would be in the Dev layer (ie any testing harness stubs, etc), and some of it would be external to the product itself (ie defect tracking). However, as a Persistant RunTime Development Environment, as most MUDs are ... its almost like I need a PROJ MGMT layer to encapsulate feature planning/triage, release planning, player bug reports, deployment process, regression testing, etc as part of the produt itself. I am not sure how to model that part of the software lifecycle inside of a MUDlib. *Ponder*
PERSISTENCE - I had originally considered it part of the World OBJ Model; however, you are right ... the really cool things aren't possible unless its a major priority. In fact, its almost a DEPLOYMENT/ROLLBACK + Continuity issue. Good catch!