This is more of a def tool that anyone can use. The idea is to apply a patch to the def and object at loading time without overwriting what is there. For example: you want to change the price of the butcher table to 10 wood from 20 wood as the base. You would want something like this.
@def[butchertable]
@WoodLog = 10
or something like that... The idea would be is if I want to just change the wood cost without effect the rest of the butchertable I can or if someone wanted to change other things they can without effecting each other. this could be made into a mod that allows people to copy parts without really coping the whole part into a new xml. There is greater things that this mod could do...
Now this isn't a new idea... for those who play kerbal space program and likes to mod it. This comes from the mod Module Manger, which pretty much every mod uses.
Is this doable?
Note: I sometimes(most) have a bad lack of understanding about things, but I'm pretty good at being corrected(just ask my wife)
Wouldn't be possible as a 'mod' really. Would require changing the core game files, or generating entire mod folders for specific things. So the lazy answer is no.