I do make a welded construction but for the manufacture our subcontractor needs to have all the parts separated and this is only possible by having "register the bodies" on the list of welded parts to create an assembly with each profile a new part
I don't understand your subcontractor. We are too and we receive plans for the welded construction of the chassis with their markings on the MEP and the part in Sw because we are in 2016 and then we make the MEP details for manufacturing as we wish. Depending on the chassis it takes us 1 to 2 hours but at least we have our plans as we want with the right information on them... It's not more complicated.