This is not a proper head-canon, it’s more of a random idea I have.
A lot of fans of the Knights of the Old Republic games seem to dislike what Bioware did with Star Wars: The Old Republic. They don’t like the way they treated Revan’s character in the novel and the game, they don’t like how many times the Sith Emperor resurrected, as well as a lot of the other plots that were developed in the MMO. However, I recently came up with an idea that can more or less attempt to satisfy the Knights of the Old Republic fans that were disappointed with The Old Republic. And my idea is very simple: taking the first three cinematic trailers of the MMO and building a story around them, without necessarily accepting the Revan novel and the rest of the game.
Think about it…
In Knights of the Old Republic II, it’s revealed that Revan knew about a Sith Empire in the Unknown Regions, and turned to the Dark Side to conquer the Republic, make it stronger and prepare the Galaxy for the Sith invasion. Okay, perfect. Then you have The Old Republic: Return, where the Sith return and invade the Galaxy, indeed, thus confirming what Knights of the Old Republic II told us about the Sith invasion. That cinematic alone makes you understand that the war with the Sith has started. After Return, you have The Old Republic: Hope, which shows the Battle of Alderaan between the Republic and the Sith Empire, and also shows that the Republic wins the battle. That cinematic alone makes you understand that the war with the Sith is raging across the Galaxy. Finally, you have The Old Republic: Deceived, which shows how the Sith Empire invaded Coruscant. Since the Sith Empire successively invaded Coruscant, you can assume that the Empire won the war and conquered the Republic. But, since we know that there is no Sith Empire when Darth Ruin turned to the Dark Side, you can reasonably assume that the Sith Empire fell apart some years ago due to the continuous internal Wars between the Sith, and therefore the Republic was restored (which is more or less what happened in the Original Trilogy).
So, as you can see, using the first three Old Republic cinematic trailers is more than enough to create an entire story without necessarily having to accept the canonicity of the Revan novel and the MMO itself. Besides, you also don’t have to accept the fact that the Sith Emperor resurrected at least a dozen of times, and you can still keep Revan’s original motivations intact. Furthermore, using this idea would also allow you to explain Palpatine’s line in Revenge of the Sith about the Sith ruling the Galaxy once more (which means that they ruled the Galaxy in the past).