I think you underestimate the distances involved. It'll be impossible to maintain the infrastructure. How are you going to get these people there? Additionally, You will need an enormous number of tugs. It's' not like there are clearly marked highways or anything. The area to be covered is going to be huge. What are they going to do in bad weather? Then, who is going to coordinate all of this? How do the tugs know where to go and when? If the weather is bad and there is no fresh tug available the ship will go down. Let's not even talk about how inefficient and slow this will be.

The forces of nature these ships work against are nothing to sneeze at. This stuff is not at all trivial.