While it would be possible, they would make no money off of a server like that, so unless they have a cash shop where you can pay to unlock cosmetics or something, they won't make money to keep the server alive if all the "F2P" decide they don't want to play on any other server.

Only way something like that would make sense for the company is if they could charge a subscription fee for keeping that kind of server going. Say like $5 a month or something. Which isn't "free" but it could remove all aspects of paying for power or ninja to make it more balanced.