We're long past the point of needing to use the same few 3d objects for everything - that was needed when the game was first created but isn't needed now.
The new worlds which are lush and full of variety proves this.
So how about redesigning marleybone?
It makes some sense for Cats to be wandering around on rooftops, but dogs? And mice? Mice should be inside the walls, cats should be on the streets and alleys and rooftops, and dogs should be on the streets and in back or front yards.
There are all sorts of sidequests that could be created in marleybone for the newer worlds too - not just a couple of boss battles in towers or warehouses.
And while Sherlock has the correct address, and even a living room, Scotland yard is not scotland yard - it's a rooftop with a couple of animal cages.