Shouldn't the biju be allowed free if Naruto really wants to help them?
You don't have to be a Jinchuuriki to befriend a Bijuu. According to Naruto, he wants to partner up with all the Bijuu, even though not all of them are sealed inside of him.

He can't really change his situation with Kurama since extracting Kurama from him will mean the he would die, however Naruto means that Shinobi and Bijuu can be allies/friends like Shinobi and other Shinobi.