Can you define PW System.
Do you mean Persistent Journals, Database Entries, Quest systems etc?
In any case, I would recommend nwnx - to add most versatility.
nwnx_areas - for instance, is great for creating instanced areas, important when you want something like player homes.
nwnx_funcs - for modifying player ability scores, skills, adding feats etc (without requiring the player to logout and in again)