After I spoke today with some 3D printshops I have following remarks regarding the 3D printing.
First:
It looks, that it will be a hardware problem. Not all 3D printers can print such large part at once. Probably It has to be divided into smaller parts, and and assembled like Lego blocks?
The second:
Due to the fact, that it has a big volume it looks, that wood will be the cheaper solution.