Something I mentioned in your last thread, that I feel is worth bring up again again (because it's super important):
PCs =/= NPCs.
This game isn't D&D, where "commoners" share levels in a single (and fairly shitty) class. They are built with the NPC system to the specifics of their job - so you have Craftsmen, Priests, Bankers, Guardsmen, Barkeeps and so on. Not just "Commoners". They're on page 244 if you want to see all of them.
Now: a commoner Craftsman, with Crafting VII has a +8 to Craft checks. This covers Common meals, as well as Filling and Comfort food (along with animal food and alcohol).
PCs will not have straight 10s, so that assumption is a little flawed, and if the PC wants have Int as a dump stat then they shouldn't be surprised that they are crappy at Intelligence based skills. That said, I agree that a Common meal has too high a complexity (I run it at 5D, same as Comfort food).