IMO, it's either all, or nothing. I don't think that adding a cross-world NPC would do justice to both Tolkien and Silmarillion. It will be a bit like 'who would win the battle: Irenicus or Feanor?' type of thing. Tolkien's characters are designed to live in Tolkien's world, with their motivations, laws and mentality. So, yes, the TC initially suggested is the way to go imo, but it is a long-long road (no pun intended) and requires many a skill.