I'm surprised Maninga is the only one who mentioned the need to fit into a shipping container. For an "around the world" travel rig, container shipping saves a lot of money and is much safer for the vehicle and it's contents. There are many horror stories of vehicles being damaged and broken into shipping roll on/roll off. Even just traveling the Pan Am, now that the ferry is done shipping around the Darian is easier and cheaper if the vehicle fits in a container. For reference, a 40' HC is about 8.5 feet at the door opening and a standard 20' or 40' is about 7.5 feet.
I think for a lot of people, it just isn't a concern. When I think about it, we're only planning on using a container maybe 4 times (Aus - US, Panama canal, South America - Europe, Somewhere - home). Yes, it's cheaper to ship, but can be more expensive to build so may even out. I think you're going to have more risk with a traffic accident or getting stuff taken while on the road.
While at the start I was thinking container was a priority, and will with some work, realistically I'm more concerned about fitting under some low bridges on commonly driven routes.