I have though about this house rule, which adds a little more realism and open the door for more trade opportunities.
I personally have never liked build this and it will build the ship and the components will be build in space on the shipyard. I always liked the idea that components should be manufactured and then placed into the ship. There are some components that cannot such as geo and grav sensors, fuel tanks etc. However it would be nice to see some surplus system.
It will add more options for trade benefits as well.
We can add this now as there has been very little space activity.