Sketch in assembly and break it to parts

A lot of the times I'm conceptualising a hole component in a "sketch" mode and than have to start new string of sketches in order to break it down to its core parts, a crazy powerful tool would be if you could break this component into parts, the original sketch will become an assembly of all the parts that created it, the parts will be opened than in their a sketch mode so: 1st. It would be easier on the hardware and 2nd. You could dive into each one and fine-tune it to your needs.

You should be able to turn off or on relations between any of the parts between themselves or the assembly. You should be able to add more parts to the assembly. You should be able to replace a part with a newer part within the assembly