Standardization is cool, but it is a different feeling when you load into an environment that looks like an actual, lived in FOB opposed to a generic one. Not to mention with a functional and good looking FOB/COP, you can actually make missions around it. (Eg, TForce spawns in not knowing what the operation is actually going to be, and just create a developing situation - results in the FOB/COP being used realistically, providing immersion due to the fact that it looks immersive and the factor of unknown threats puts the players on an edge)
Sort of how we did it this operation cycle. FOBs and COPs actually feel like FOBs and COPs, instead of a default 'you are safe in this vanilla looking staging area' type of base.