If you could pick to eliminate two of the Ravnica guilds, which would you pick (assuming you want the city to function as well as possible)?

I honestly think that the easiest to eliminate are Gruul, Selesnya, and Dimir. Gruul serves very little purpose in the plane, except maybe to prevent the guilds from becoming complacent (and they did that anyway). Selesnya is just a cult: if they were eliminated, the plane would lose some of its national parks... and basically nothing else. Almost nobody knows Dimir exists: if they were gone, most people's lives would continue exactly as they were before.

Compare that to the loss of Azorius or Boros (no government or law), Orzhov (no money), Rakdos (no freedom of speech), and Izzet or Simic (no technology), and I think there is a good case to be made for eliminating those three guilds.