What I mean by this is moving blocks in a specific path that the builder sets. First thing is first, how to switch between paths and normal blocks. My suggestion would be a key that you hold down as you build the block, such as P for path, or anything. Next is how the player would set the path. Well, lets say he puts down a blue block and makes it so that it is a path block. A temporarily line, only visible by the builder, is shown. This tells you which way the block will be going. The lines would be the length of a normal block. You set the path, and then just hit another key, probably left click again. That would signify that this location is where the block ends its path. To expand on this, i also suggest that once the path is set, the builder needs to set the speed of the path and if the path is triggered by a player or just goes by itself. For deleting the path, you simply delete the block.
Sound good? Please give feedback.