Be Inspired!

The "Beyond" Stuff
There is a strong reason why ODD is my favorite flavor of the game. It demands input from the would-be referee. More so than its OSR clones and simulacrum, more so than all later editions called "Basic" or "Advanced", the three LBBs in the White Box demands you make it "your game" by adding to and customizing. And by doing so, you inspire others to make their own game too. It is a creative catalyst for gaming. That is how it worked in 1974 and how it works today.
There is probably a reason (or two...) that TSR continued to support the original game through the "Basic" product line long after "Advanced" was released. The tournament friendly version of the game is more limiting, more confining than the version most directly descended from the original three LBBs and bearing its simple ampersand name. Why two parallel product lines within TSR? Because they each supported a different vision of the game and met different goals. One is introductory, aimed at home play and presented as guidelines open to personalized modification. The other emphasizes homogeneity and allowed for tournament play with standardized rules.
When WOTC joined the two product lines into one, something was lost in the process. Official sanction of the "rules as guidelines" philosophy has been abandoned, at least until 5e where it is getting some recognition again as a non-heretical, alternate play style. Personally it is a play style I have never abandoned and have brought to every rule system and setting I have ever used in role-play gaming. I treat just about everything I read, rules, setting material, and literature, as guidelines and inspiration. It isn't the only way to play, but it is my way.
So what about Middle Earth? How much must we adhere to canon? Are welimited to only that which the Professor wrote? I like to imagine things beyond what is written, but keeping with the general feel of the material. So in my M.E. there are "witch-priests" who are drawn to the power of the "black arts" and who align themselves with the forces of darkness... For me they represent those whom I imagine to have embraced corruption and are willing to serve the Shadow. (Is this not what Saruman does?) It seems plausible to me that ordinary men/women, being flawed humans, might act this way and earn the name "witch". Did the Istari ever teach men some magic? How about the Elves? Can there be mortal men/women, who having studied the art under greater beings, begin to dabble or even master some forms of magic in your game version of Middle Earth? They do in mine.
Don't be fenced in by what the author wrote...any author. Use it as a starting point and be inspired. As I introduce players to my Middle Earth game I sometimes say something like, "You have read about Middle Earth and all you read is true...but there is so much more to discover, so let's do some adventuring!"