If that's how it would work, they wouldn't need to coordinate with anyone else. Just use "login.tplink". Since it's quite unlikely that anyone else would use that TLD, there wouldn't be a problem.
how does a 301 fix a person not understanding how to type a url into the address bar? plenty of people dont understand the difference between searching and directly calling a website.
This serious problem you describe, of cavemen and preschoolers who don't know about URLs, has been solved now for a long time. 301 is part of that solution. The tp-link.com site is perfectly capable of examining Referer and using that information to help tplink users.
However, since we've already established upthread that the router controls everything about the online experience, it would be no problem redirect the first navigation through an unconfigured router to a "wizard" page.
only if you are the first result, and by first result i mean the first ad. people can pay to be the "result above you.
there is no reason to insult the people in their 20's 30's 40's 50's 60's 70's or 80's who are confused about the difference between a search bar and address bar (especially considering the major browsers merge them)
the unified bar has led to a sharp decline in people being able or caring to type correctly configured urls.
people would type login tplink into google/bing
from a usability standpoint this solution wouldnt work.