Can I Duplicate The Default Cube Mesh To Give It Different Scale Factors?

I am not a modeller and so I am attempting to build as close to a zero-asset game as possible by forming all game objects out of assemblages of cubes- so far, it looks promising as an art style, sort of halfway between Tron and Minecraft.

Unfortunately, when I scale a parent cube, all of its children scale as well, which is undesirable for the process of designing the game objects. I have been digging around and it seems like what I need is a collection of cube meshes at different scales, and I really do not want to have to start messing around with modelling software just to get some cubes. Is there a way I can duplicate and manipulate the default cube itself? I have been digging around but so far it seems inviolate.

A method of manipulating world scale instead of local scale would work as well, but I haven't been able to find that in the interface yet. Also, I am concerned about the performance implications of having most transforms scaled at most times while the game is running.