It has already dawned on me, there are two distinct paths to follow here, which represent most members of the railway modelling community. This affects how a vehicle should be produced. It is a reflection of the situation with white metal kits 60 odd years ago.
So the two choices are, one piece complete body shells or a kit of parts to assemble. Either can be designed to suit RTR chassis or printed chassis can be provided.
Whilst a one piece shell is attractive for those who feel they may not be able to assemble a kit, a set of parts maybe more practical to allow for variations within a class of vehicle. The latter would dependent on the quality of the design and the tolerances of the printer used. As Rob has shown, not everything already available is correct. This is a reflection on the Designer and what this person believes is correct.
As for the time required to print, it seems slow, but I appreciate, you can go off and do something else. The newest printers have a built in camera, so you can always keep an eye on the process via a smartphone. I have pondered whether you could print off a set of masters to make a mould, or you could just print a mould and cast items from this.
The options and possibilities seem endless. I really need to get some equipment and give it a try.
Paul