I just had a bass built for me by Jean Auray, and it is fantastic. You can check out his
detachable neck system here.
He has made basses for Charlie Haden, Renaud Garcia Fons, Henri Texier, and many orchestras in Europe. He makes very high quality instruments. The neck is very secure and it seems like a solid system. Very easy to take apart/put together.
The sound of the bass he made for me is fantastic, plus he made it exactly to my specifications. He sells it with a flight case, which is about the size of the body of the bass. The neck, strings and tailpiece go in a separate case that attaches to the main case. With bass, the whole thing weighs just under 30 kilos, which is about 65 lbs. It is oversize, but not overweight. With other trunks, my old bass weighed around 100 lbs.
The only problem is that Jean has quite a waiting list at the moment. He lives near Lyon, in Ville-Franche-sur-Saone. If you are going to be in Italy, it might be worth a trip north.