well i mean, load a build as a static object (option next to public) and pick a color for it. The bricks you load are the same SHAPE and have simplified collisions as the build but all one color. you oviously couldnt edit stuff loaded as a static object
The problem with that is that with a really huge build like, say, Seattle, it's better for it to be separate blocks, since you can lower the draw distance and not have to render all the faces at once. With it being one block, all those faces would have to be loaded, regardless of how far your draw distance is set.
TL;DR: Huge builds would cripple all but the top few systems playing Blockland.