It is very very rare that we need to use a Body in an assembly, so why not make a Component in default from a sketch?
If somebody wants to make a body then let him select Body else whenever one Extrudes/sweeps it should always create a component.
It is so excriciatingly painful when you learn that you have forgotten to make a compnt in a big assembly. Coz when you go back and make that body into a compnt then the whole assembly collapses and you have to start all over again...
