I agree that Mark's view of NERO is limiting. But it's a very good and necessary limitation. It doesn't prevent things like politics, merchants, and crafts. It just makes them more have to be more realistic. When you're "on the edge of a city" you're not playing NERO any more. You're playing Minds Eye Theater. NERO is designed to be physrepped and immersive. It's not designed to be highly imaginative.
When games are run where more exists than you physrep you run into the major problems that many players had in the seattle game. No one know what existed, where it was, and how accessible it was except for a small group of people that were very close to plot. There were estates, towers, keeps, docks, and all sorts of things that people were interacting with that didn't really exist. That's not NERO, that's tabletop. If you want to play a shipping kingpin and own several hundred guards, find a dark ages game.
Nero is based around the idea that everything should be presented in game. I don't care if your character has 10 personal bodyguards unless they show up in game. If they don't show up he might as well have 10,000,000 bodyguards. It won't make a difference unless they exist in game. Mark's view is limiting because you can't ride a dragon, or hide in a keep. But it's more fun because everything you need to interact with is real. If someone is holding a sword, they're holding a sword. If they're standing over there... they're standing over there. If they have coin, it jingles. If they trap their house, there's a trap at their house. These are the tenants that NERO is based on. It's not designed to be a game where "anything is possible". Inspire of it's motto you're not supposed to be everything you can't be. You're supposed to be all that you can be in game.