This sorta sounds like a PC104 where one stacks n-number of boards together to get something you want. Yes, the original board is small, but start adding the options you want and the thing gets huge. Let me get a small basic stamp and add a whole bunch of stuff on it to do what the one 8051 board does already. Next thing I see is a long rectangular volume. These things do not add value. Why not just PC a board you want to minimize the volume? Or just make your own USB programmable chip carrier with an 8051. There are plenty of low pin count USB programmable devices where you can just attach pins. Still yet, does not buy you anything other than modularity and is mostly inefficient. All of those chip carrier boards are mickey-mouse and are just out right not used in the real world. They may be good for developing or learning, but beyond that.... thats out to lunch. I'm sorry but couldnt one just get a USB 8051 slap on a connector on a board and make it USB powered? But I think thats just taking modularity to the extreme.