The way it worked is there were 10 prefabs. 9 equal sized pieces and a 10th outer wall.
Each inner piece had doorways at the same spots, but different interiors. Setting up the mixer (well, stompy did most of the work) made it so that ONE of the 9 pieces would spawn in one of the 9 spots, with a random rotation, until all 9 were filled then the outer wall was spawned. Voila, instant random maze.
You could do a building the same way. First the outside shell, then individual components that spawn in the interior, that could connect together to make rooms. As long as the connection spots lined up, it would work.
I doubt you would need to take this approach to your idea though.