First of all: What are all 8 Spells of the Necromancer if not the ones of an aggressive caster / nuker? (Apart from that: Direct magic and Tolkien... Possible, but hard to maintain the right amount.)
Secondly, if Sauron was given the possibility to recover his old self, including his body (coming with the ability to shape-shift) and all non-ring-powers and able to roam the earth freely OR take the form of a dark shadow roaming Mordor... Hope you see the logical problem in such a choice: Gorthaur being historically Sauron's true, undestroyed and complete form can't possibly bow to his destroyed shadow he was after only his spirit survived Numenor's fall.
Thirdly, and IMO the most glaring problem: Why stop there? Maybe some people don't like Aragorn becoming king and prefer an alternate dimension where Denethor becomes a good guy and Aragorn doesn't become king? Or another version, where Thorin is visibly older and looks like the old Edain-model? Or another interpretation of Smaug where he is a wyvern? Or -how about this?- a version where the Easterlings are free from Sauron's influence and serve Gondor instead? Following your logic these are all good suggestions because all of them are easily implemented, don't take away anything and are nothing more than an offer to the player to chose from. And this would end up as a terrible mess! Of course the ET could implement tons of choices to be made by the player in one game. But this would cause complete overkill to the game and drown every single usefull gameplay development. I know you didn't ask for this. But your idea kind of stands out as an epitome for such a suggestion!
Greetings
Melkor Bauglir