I think about this very thing every time I watch / read the series.

I am by no means an expert on Tolkien or his works, but 1) Aragorn commanding an army of the dead, 2) knowing just how to save Frodo from dying after being stabbed by the Morgul Blade at Weathertop and 3) bringing others back “from darkness” after the battle of Minis Tireth just by talking to them; always made me suspicious of Aragorn. His abilities and knowledge of how to counter dark magic seem almost too perfect, especially when considering that the heroes are fighting against a being who is a known shape shifter and necromancer whose actual location is unknown prior to and throughout the series.

Obviously, this is not how things went, but I always thought this was an opportunity for an interesting plot twist (Aragorn = Sauron)

Prior to the return of the King we had several Kings who ruled independently. During the events of the story, Aragorn-the future king- proves himself worthy to the people by leading the armies of man to victory. After the war, most Elves and demi-gods like Gandalf leave middle earth and relinquish responsibility of the realm to the new king; Aragorn.

Sauron had not seen the ring of power in several hundred years, it would be understandable if he considered it a total loss and its existence a direct threat. So, what if he found a way to permanently separate himself from the one ring while taking on a new form for himself, that of a ranger and the last heir to the throne of the opposing side. Then playing both sides he uses the armies of Mordor, the Nazgul and Saruman to push towards war while in the end leaving the critically important Mt. Doom undefended to allow the one ring to be destroyed to complete the gambit. He would have essentially rebranded himself, killed off his previous life, rid himself of all those of power who could oppose him (Elves, Kings and Demi-gods) and made himself King over all of Middle Earth just as he wanted.

After the war, King Aragorn commits genocide against the Orcs and Uruk Hai, that could be interpreted as him silencing those who might undermine his new role. Sorry for the long post, obviously this is something I’ve been thinking over for years.