That's a pretty bad article. The writer couldn't have done even the slightest bit of research, relying instead on half-remembered fragments of comics he read a decade or more ago.
Apparently when it comes to Rebellion developing games from the 2000AD IP they own:
have no previous experience in creating such content
...apart from the Judge Dredd and Rogue Trooper games
*ahem*.
The author also thinks that producing the entire city is infeasible, but that as it's naturally split in to four parts (the compass points) then a quarter of the city would be easier, with the rest to be developed later. Setting aside that the city has a Central region in addition to the compass points, plus the NW Hab Zone, a quarter of the Mega-City would still take a lifetime to develop to a playable degree. No mention is made of sectors, which is a more manageable MMORPG size, or blocks for a smaller game. The best fit for a sandbox game would be the afore-mentioned NW Hab Zone (Sectors 301-305, depending on era) or the Pit (301 alone), as it also has a game border edge in the form of the radzone surrounding it.