There is no problem staying our of US for more than one year as long as you register with the American embassy in Japan. The problem here is really to get inside the country with a long visa...
The cultural visa would not really limit your ability to travel, as once you are in the country, no one will check what you are actually doing. I guess if you can prove that you have resources to stay one year in Japan without work, this would help. I would be more careful about posing as a freelancer, as there might be some background check one your work; also, I think there is a journalist visa that is reserved for professionals, so if you pretend to be a writer, you might be asked to apply for such visa, and then you really will need a sponsor.
But we would be delighted to read from you on this web site, even if I think we don't have the strength to sponsor you for a visa
sanji