Regarding moral ambiguity, let me see if I can explain my thoughts and then tie them into role playing in Middle-earth in The One Ring.
Tolkien's works always appealed to me because it was a morally clear world. As Robin described it:
I realised that Middle-earth as Tolkien describes it is a more Moral world than ours - ie good gets rewarded, bad gets punished and things don't happen for no good reason, unlike in our world. Within this broad overview there are times when black and white becomes 'blurred' such as during the Kin-Strife, but generally Right & Wrong seem clearer than in our world
In the Christian world view (as I see it) it could be said that true morality is absolute and sharply defined. There is Good and there is Evil (that which is opposed to the Good). At the beginning of creation, that was all that existed. Any blurring of those lines is not the result of an alteration of absolute morality, but more the result of the entropy of countless imperfect individuals acting in free will over time.
I can envision an old-school slide projector. There is a "perfect" image on the slide. Light passes through this slide and then carries a copy of the slide across space and time to produce an imperfect image of the original. In the process, the light diffuses and the image become out of focus, more so the farther away from the "perfect" original you get. You can still get a sense of the general idea of the original, but the edges are all blurred. This blurred projected image does not mean that the original was not perfect, it just means that the viewer perception is imperfect.
I think that Tolkien, writing with the influence of his Christian background created a world that is truer to the original than what ours is, but it is not a perfect world either. There is still some blurring of the lines between Light and Shadow because individuals have free will.
There are creatures who are created morally pure (Elves, Men, free peoples) and those who are created inherently evil (orcs, trolls). I would argue that orcs don't have free will in Tolkien's world, because they cannot choose to do good. Men and Elves on the other hand can choose to do evil and reject good. Orcs and their lot cannot be redeemed, but the Free Peoples of Middle-earth are never entirely beyond redemption.
In The One Ring, a "good" character can be affected by shadow either through their own actions or the actions of others and gain shadow points, but there is some spark of Eru within them that drives them to seek the good. Elves seem to be more resistant to the corruption by the shadow. Men seem to be more lured by the promise of power or wealth and more easily blur the moral lines. Maybe that is due to the fact that Elves are immortal and remember how the Shadow destroyed all they held dear while men live such short lives comparatively that generation after generation falls for the lies of Sauron.
I like that in the One Ring, a player could make an evil character, but he would quickly be overwhelmed by the shadow and no longer be playable. Such men existed in Tolkien's world, but they were similarly destroyed by that which they sought after (the Ringwraiths for example). The heroes in Tolkien's books were those characters who imperfect or flawed as they might be kept the absolute morality of the Eru's original design in focus and sought to advance that theme. Their heroism wasn't dependent on their success or failure, but on their motivation. Ultimately Eru's will would be accomplished and even those who fought it would contribute to its fulfillment. Each character just had to chose their side and do what they could in their sphere of influence.
I player who understands this going into the One Ring will, in my opinion, enjoy the game much more than a player who wants to make a character become all powerful or change the world. Tolkien's characters generally didn't want to be heroes and those who did (Boromir perhaps?) ended up getting off track.
Don't take this too seriously. It is just a few thought I had. I am no expert in theology, philosophy, or Tolkien.