This idea is not late by any means, I don't hope for its implementation or even seek developer acknowledgement - I'm posting this as a "should have done" scenario with a "maybe they'll see the light" mentality.
And the players that would populate this third faction would be those interested in fighting both republic and empire alike - this faction would serve as the X-factor in the balance equation that would allow the player population to sole the problem.
And I know is hard for most people to accept star wars without all the Jedi but my favorite times in SWG were before the first Jedi ever even unlocked.
Again, this isn't a "give us" thread, just a "what if they tried this"
Feel free to throw in other ways to fix the obvious faction balance issue.