I don't really like the idea because we already have enough things to bake. We need more foods for the frying pan! Omelettes, meat & onions, stuff like that!

Besides, as it's been pointed out, to have a decent pizza either olives and olive oil would have to be added (which isn't a bad idea in itself), or tomatoes would have to be. I think the more accessories you need to add to the game, to get a specific item added, just adds more potential trouble. You can add a lot of different new foods using ingredients that are already-in game, but pizza isn't really one of them unfortunately.
Hearthlings: Marona; Chamberlain (retainer alt), Vincavec (shaman of the Dryad Wells Forest)