You suggest an assembly within another assembly.
It is not efficient, nor practical, for a serial work of hundreds of drawings.
There are already many drawings made, which must be modified. too much work.
Besides the fact of creating a new assembly or changing an old one, let me say that the task You are trying to solve more is an issue of ERP rather than CAD as You try to achieve.
So use CAD, but use it easy and fast or go to the ERP!
This would be my advise.