There is an optional component of L1NPCs that lets you change references to the NPC's profession, within certain boundaries. It helps if I know the dialog files where such is referenced but if that info isn't immediately at hand, I can run some sort of arcane grep in some code I've forgotten how to execute, let alone write (*grumbles in orcish*).
It's more a conceptual matter, really, than a text-string matter: Hubelpot's references to his background as a farmer or druid are going to be a bit off if they're changed to "When I was a thief in my little town" or "I gave up work as a fighter to..." as are character reactions.
Again, though, I have no problem with L1NPC adding him. Anyone who adds it has to know it's going to make for some conceptual oddities every now and again for any NPC so altered.