I've always liked the NPC classes of the 3e/3.5 system. So please don't forget them in the mad rush towards Patherfinder RPG.
I would suggest the following:
Adept
Maybe they can borrow something from the arcane schools? Divination, Enchantment seem like logical choices.
Commoner
Maybe it would be a good idea to limit the progression of this class to level 10?
Please use the commoner class as a replacement to ECLs.
(or a specialist version of it).
Allow all humanoids a "free" commoner level at creation, concentrating on the background of the PC.
I limit all npc classes to 10 levels. Not because there are reasons they shouldn't advance anymore, but because when you use NPCs of level 8 or greater, it seems apropiate to give them PC classes. More than 10 levels are simply not needed.
I always found the notion of a peasant of level, say, 10, strange to say the least. I think the peasant should be used in place of the "zero-level human" of AD&D2, and execptional individuals represented by the other NPC classes.
Stefan