Apsara, Is this a machine that's being made to sell or for personal use?
If not for sale, could you provide an exhaustive list of parts needed and instructions so others could make one?
I make and sell these machines, this one is designed for milling foam. I charge $3,600 for the machine which is a fair price considering other machines on the market are $6,000-$8,000 for a table this size. Size of the table is a 4x8 with a 24"z axis and comes with electronics and motors ready to plug in to your computer. I also have parts available as a kit with instructions on how to put it together. When I have my website up you can buy parts off there, parts are very affordable.
Yes you can attach a print head to it, for it to work with the extruder you just have to change up the software and its ready to run. During the summer I will build a full scale version of a 3d printer for printing large scale items such as cars, boats, motorcycles, maybe a new girlfriend that doesn't talk back lol
Using a printed body panel is very weak for a car body, even if you add thickness to it, it will still split on the printed lines. It is only good for rapid prototyping of an object.