[jrq]

That's not practical, the high sea can be incredibly dangerous, even with modern nautical technology. Most tech out there is informational, there's very little you can actually do if the ocean decides to throw a tantrum.

Also, ships don't just go to waste when they reach EOL, if they do. They get scrapped, similar to a car I guess, but a lot of material can be reused or recycled or sold, and so on.

Anyways yeah, giant tugs, not a good idea. Not a good use of resources.