In an .idw, allow an overlay on weldments to be able to show different view representations or a different weldment state (weld, machine, prep).
Quite often it's very helpful to show a phantomed outline of what the pre-machined weldment looks like on the machining drawing. As well, on simple weldments or things with only a small amount of machining, the welding and machining drawings could be combined to save making a drawing.
I'm working on a drawing right now that I'm trying to show how I want a customer's existing weldment modified by cutting away pieces, and having what it looks like pre-modifications overlaid in reference lines would make what actual work needs to get done much more clear. I could also specify "how much material to cut off" rather than "how much is left."