It isn't something I tried to stop, because of a historical map I saw with some farmland inside a wall much like this, but I do think it is kind of strange. I'm not sure they'd want to rebuild it that way the first time the outer buildings get burned, so I'm also not sure if it'll last up to the army stuff, but I'll have to look at more example images from history and whether the one I saw was a total anomaly. It should probably prefer to fill out the interior -- right now it just spills out buildings from the keep area.
I'm not sure if it's a reliable historical reference, but I was reading "The Hunchback of Notre-Dame" and it had a section that told a little history about the architecture of Paris.
Basically, several times in the history of Paris, attempts were made to build walls to encompas the entire city. Most were relativelly unsuccessful, and those that were, were only successful for 50-100 years. The tactics to do this, were restricting the building outside city walls, and building another giant section of the wall extending way beyong the city. Eventually, the shops and houses got too crowded, and spilled beyong the walls, which triggered another round of wall building in a couple decades. But for a short period of time, there was empty space that was not filled with anything.
Basically, the moral of the story, is that a strong ruler wants to protect his city and commands a wall to be build around all the buildings in the city. Of course, he can fail depending on his personna and the layout of the city, but the desire to have some empty space is not an anomality. So as long the empty space you have is rare, or quickly fill up, the stuff you have there Toady, is totally legit. Of course, Threetoe probably knows about this more than I do, but I think it's totally legit.